Riichi mahjong strategy
Fukuchi Makoto
translated by anon
Introduction
This is a translation of a html book by Fukuchi-pro, author of 現代麻雀技術論 (Modern Mahjong
Strategy Theory). Since Riichi Book 2 by Daina Chiba probably never, I started translating this one,
since it’s extremely comprehensive and detailed and has both abstract theory and many examples.
It’s by no means a word-for-word translation: I’ve added examples to make some points clearer,
and omitted some passages that were redundant or unclear. If you can into moon runes, denitely
read the original at http://yabejp.web.fc2.com/mahjong/tactics.html.
So why this book and not some other one by a more famous contemporary pro? There are
several reasons. First of all, this is the book I personally used to get into tokujou. It’s about 12
years old, and some of the meta concepts have changed since then, but it’s still a good base. Second,
I think it lls an important gap between books for beginners and books for mahjong addicts who
already know the standard plays. You need to learn the standard plays somewhere. But if you’re
new to mahjong and haven’t read RB1 yet, go read that one rst, because it introduces many
important concepts in a more accessible way.
Who is this book for? It’s for people who want to git gud, but can’t into moon. If you don’t
care about gitting gud, you’ll probably nd this book dry and boring. It’s also not for brainlets:
there are many passages where you have to think hard, and if anything I’ve cut down on the
explanations instead of expanding. But don’t worry: even if you understand only half, you’ll notice
a big dierence once you start playing. You just start thinking about the tiles dierently after a
while.
The book is heavily focused on tile eciency, with a highly digital (analytical) way of thinking.
All of the later material about push-fold judgment and discard reading is based on good tile e-
ciency. People often claim they know tile eciency, yet they can’t solve simple WWYD problems.
I’m a Tenhou 6d and among the higher IQ gaijin players, but I still have trouble with (say) G.
Uzaku’s problems. Tile eciency is hard.
I’ll try to translate roughly 20 lmao more like 10 pages a week, we’ll see how it goes. Just (you)
me in the thread or PM me on IRC (Sjaalman) if you have a question or opinions about this shit.
Desu I just want to help everyone git gud, because I’m a tryhard and I think it’s more fun that
way.
t. attention whore
Contents
Contents 1
0.1 Outline of mahjong skills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
0.2 How to get good . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1 Tile eciency 9
Principles of tile eciency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.1 Tile logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Discard choice method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Isolated tiles and simple joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Comparing pairs and bad shape joints . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Complex joints I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Complex joints II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Ultra bad shape joints and furiten joints . . . . . . . . . . . . . . . . . . . . . . . . . 19
Comparing components of the same class . . . . . . . . . . . . . . . . . . . . . . . . 20
Penchan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Outer kanchan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Inner kanchan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Ryanmen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Pair dropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Isolated 1 and 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Isolated 2 and 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Isolated 3 to 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Joint dropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Comparing simple and complex joints . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Comparing isolated tiles and complex joints . . . . . . . . . . . . . . . . . . . . . . . 40
Complex groups (many-sided waits) . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
1.2 Head start tenpai judgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Understanding tenpai eciency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Head start riichi judgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Win rate maximizing damaten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Defensive damaten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Wait improvement judgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Wait choice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
1.3 Calling eciency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Calling tile logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
1
2 CONTENTS
Calling judgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Planning yaku for calls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
How to make open yaku . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Principles of calling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Dierences from closed tile logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
1.4 Yaku composition techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Principles of yaku and dora . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Tanyao . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Pinfu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Iipeikou . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Yakuhai pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Single yakuhai . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Sanshoku . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Ittsuu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Toitoi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Chiitoitsu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Single suit hands (honitsu and chinitsu) . . . . . . . . . . . . . . . . . . . . . . . . . 78
Chanta, junchan, honroutou . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Sanankou . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Kokushi musou . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Nagashi mangan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Dora in closed hands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Dora in open hands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Atoatozuke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Formal tenpai . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
1.5 Iishanten eciency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
The importance of being rst to tenpai . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Classication of iishanten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Extra tile shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Perfect iishanten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Extra tile versus perfect iishanten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Understanding tenpai chance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Headless iishanten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Extra tile versus headless . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Perfect versus headless . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Sticky iishanten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Perfect versus sticky . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Returning to 2-shanten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
2 Push-fold judgment 109
2.1 Dealing with non-tenpai opponents . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Choking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Dealing with getting choked . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Discarding good tiles rst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Early game defense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
2.2 Folding techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
CONTENTS 3
Betaori . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Eectiveness of wait reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Coping with having no safe tiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
2.3 Dealing with riichi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
The average score of riichi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
When in tenpai . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Choosing the wait against riichi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Dealing with 2 riichi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
What to do in borderline situations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
When in iishanten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
2.4 Dealing with open hands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Characteristics of open hands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Tenpai estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
Defending against specic yaku . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
2.5 Supplement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
Push-fold judgment just before a draw . . . . . . . . . . . . . . . . . . . . . . . . . . 123
Rolling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
Ippatsu disruption and haitei shifting . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
3 Reading 127
Principles of reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
3.1 Counting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
The 1/18 rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
Honor waits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
3.2 Discard reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
Types of discard information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
Sobaten riichi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
Gyakugiri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
Call reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Dora discarding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
Joint dropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Pair dropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Yaku reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Sobaten tanki . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Chiitoitsu reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Eective wait reading situations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Hand progress reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
3.3 Wall reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Advantages of wall reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Tile group reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
Suit reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
Reex reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
3.4 Supplement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
Disguise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
Gyakugiri II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
Lag reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
4 CONTENTS
Tile arrangement reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
Person reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
4 Point situation judgment 147
Principles of point situation judgment . . . . . . . . . . . . . . . . . . . . . . . . . . 147
How to think about expected placement . . . . . . . . . . . . . . . . . . . . . . . . . 148
Scoring techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
How to ght in all last . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
Declining wins in all last . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Speed maximization techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
When to attack fast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
Calling when a comeback is uncertain . . . . . . . . . . . . . . . . . . . . . . . . . . 151
Push-fold judgment in all last . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Push-fold judgment one hand before all last . . . . . . . . . . . . . . . . . . . . . . . 153
How to make mangan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
What to do when far behind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
How to play when a player is close to shadowrealm . . . . . . . . . . . . . . . . . . . 155
Riichi sticks and honba . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
When to call kan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
0.1. OUTLINE OF MAHJONG SKILLS 5
0.1 Outline of mahjong skills
The nature of mahjong is repetition of choice and lottery.
—Kihara Kōichi
In these lotteries, the will of the players plays no role. That is to say, they are completely
random.
Through choices, it’s possible to make the lottery more favorable. Only
there is there space for mahjong skill to enter. Afterwards, one can only
wait for the result of the lottery.
Now, what kind of skills are required to win at mahjong (maximize expected income per han-
chan)? We’ll categorize them as below, and consider the optimal strategy for each in turn.
(1) Skills directly related to discard decisions in themselves
Tile eciency (includes score eciency, yaku composition techniques, whether to call riichi
with a head start, calling judgment)
The skill to maximize (win rate × average score) + (expenditures when we don’t win)
Folding
The skill to minimize (deal-in rate × average deal-in score) + (opponent tsumo rate ×average
opponent tsumo score)
Choking and rolling
So to speak, the skill of tile eciency when considering opponents’ interaction with discarded tiles.
(When they’re not in tenpai for choking and when they are for rolling.) A kind of in-between
strategy between pure eciency and folding.
(2) Push-fold judgment (including riichi and calling judgment when an opponent is
in tenpai)
Judging which of the three strategies in (1) is best.
(3) Point situation assessment
(1) and (2) essentially aim at maximizing expected income from a single round. But in mahjong,
nal placement is also important, making round expected value 6= hanchan expected value. These
skills complement this disparity.
(4) Reading skills
Mahjong is a game of imperfect information. While (1), (2) and (3) tend to be based on known
information, these skills aim to complement them with deduced unknown information to increase
their accuracy.
Wall reading
Assists with tile eciency in (1).
Wait reading
Assists with (2).
Yaku and hand progress reading
Assists with (2).
(5) Improvement methodology
The four previous skills are used in actual play. This skill is about how and how much to practice
them and how to use them successfully in practice.
6 CONTENTS
0.2 How to get good
Knowing strategies is important, but being able to successfully put them into practice is just
as important.
The single most important strategy is deciding whether to attack or to defend.
Beginners should focus on either completely attacking or completely folding depending on
their push-fold decision. Intermediate strategies are less important to master and much more
dicult.
It’s important to use all available information (own hand, discards, dora, opponent’s calls,
point situation, round etc.), but this information is not all equally important.
Reading hidden information should only be attempted by players who already understand the
rest.
We should always play with a concrete goal in mind. Goal push-fold decision
discard.
There are many strategies, but it’s best to learn the most important ones rst.
The most important strategies other than push-fold judgment are tile eciency of good hands,
whether to call riichi, how to fold, how to deal with opponents’ calls, how to evaluate score
dierences.
It’s important to practice in order to make less mistakes, but it’s impossible to never make
any.
In the same situation, be consistent and play the same move.
It’s good to work on skills we’re good at because it’s easier to get motivated.
But it’s better to work on skills we’re bad at because it will improve our play more.
To nd out what we’re bad at, we need to use long-term data.
Watching strong players play can be good, but only if we focus on particular points that we’re
bad at.
Once we know how to overcome a weakness, the best way to do it is to play many games.
The combination of real play and study is the fastest way to learn.
Don’t play dierently just because we’re on a losing streak.
Always review the paifu after a game.
When running out of time too often, we should think about what to discard during opponents’
turns.
When making many careless blunders, we should think longer during our own turn.
0.2. HOW TO GET GOOD 7
We should remember that mahjong is a game of chance and not get mad at unlikely
events.
If we still get tilted and start losing due to tilt, we should stop playing.
When playing, concentrate on the game.
Don’t play when hungry, sleepy, sick, stressed or overworked if it means we can’t concentrate.
Take good care of our health and condition to be able to play in tourneys at inconvenient
times.
1
1
This list is a short-form summary of chapter 5
Chapter 1
Tile eciency
Principles of tile eciency
We will rst discuss the most important things we need to pin down.
By tile eciency, we mean the maximization of expected value at rst without explicitly consid-
ering opponents attacking. (The decision what to do when opponents attack is called push-fold, the
techniques for dealing tiles when opponents are attacking are called choking, rolling and folding.)
Maximizing win rate
The expected value for a round is
win rate × score + point expenditure when not winning
Accordingly, we should maximize win rate, since it will increase both terms of the equation.
What this is means in practice is, when aiming for a big hand, don’t overlook the compatible
cheap hands.
Example erssffjjk,.5567
With this kind of hand, we want to stack the dragons and draw more pinzu, aiming for honitsu.
Accordingly, we should break up ,.. However, breaking up the er rst is unacceptable,
because it’s a better shape than ,. and the wt acceptance enables us to make a quick cheap
hand.
Leaving room for choice is usually not advantageous
Usually, when there is room for a choice, we simply want to not overthink it and take the best
move. It’s not necessary to be perfectly consistent, but for each situation we want to know the
basic move and if needed adapt based on circumstances.
Often, when there is room for a choice, the dierence between the alternatives will be very
small. The typical example is a hand with several ryanmen waits where we need to break one up.
It’s usually best not to hesitate and pick one. It might backre, but true skill nds its application
elsewhere than in this kind of choices.
9
10 CHAPTER 1. TILE EFFICIENCY
Example qwwwertsdzxcvb
Here, we want to make 123 sanshoku and break up either rt or vb. We might cut t,
draw e the next turn and get tilted. However, we should reevaluate the situation coolly and cut
w next, with the possibility of 234 sanshoku.
How to think about eective tiles
When deciding what tile to cut, we should consider what tiles are the eective tiles of each tile. A
tile is called eective when, if we would draw it, we’d keep it and discard something else. If we’d
discard it, it cannot be called eective, though it may appear so.
Example qweyuagghnm334
Here, the a can be used with s or d to create a group candidate. However, the resulting
shape would be worse than anything we already have, so the tile is useless.
There are several degrees in tile eectiveness (can make a joint, can make a group, can make a
joint into a better joint etc.).
However, among eective tiles, there is a clear dierence between the ones which move the
hand closer to tenpai and the rest. We say they reduce the shanten. In general, reducing the
shanten is greatly preferable. (The number of tiles that reduce a hand’s shanten is called the
tile acceptance. The tiles that do not reduce shanten but still improve the hand are called upgrades.
We will use these terms throughout.)
Example rtuuasdghjklvb cut r
When we draw the backre y, we can cut u and make a wider iishanten. (Although tile
acceptance-wise, there is no dierence with tvb) l is bad, because sanshoku is too far away
and we lose ittsuu.
Important factors in point expenditure
There’s a huge amount of factors one needs to consider when comparing possible discards (how easy
it is to complete groups and joints, how strong they will be when they complete (good wait, score),
defensive power etc.) In practice, considering the most important factors will lead to the correct
decision most of the time. We can’t simply make a list of all the factors and give them equal weight
or we might get overwhelmed by the unimportant factors and make unbalanced decisions.
For example, when thinking of how to build our hand, it generally doesn’t matter that
much what seat we are in. It’s true that as dealer we should emphasize speed, but this is
mostly because of renchan and tsumo payments.
This factor only becomes important when thinking about whether to push or to pull, because
the probability of getting a renchan or getting tsumo’d depends tremendously on the opponents.
Especially in the early game, we should rely more on other factors (the hand itself) in deciding
how to build our hand, with only a small bias toward speed. There is really no dierence between
North, West and South seats.
11
The old saying goes that the North seat shouldn’t call to not give the dealer more draws, but
it’s questionable how much one extra tsumo increases the expected point loss. (It also makes South
and West get less draws which further balances the eect.)
However, we should keep our own seat wind until last, and shift the haitei away from the dealer
when multiple opponents are in tenpai. The eect is small, but unlike withholding calls, comes at
no cost to ourselves.
Since round expected value 6= hanchan expected value, according to the point situation there
are situations to prioritize win rate (emphasizing defense with a hand that looks dicult to win)
and situations to prioritize score. However, in most situations (enough rounds left, no one close to
busting out), it’s not really necessary to be conscious of these, and we can ignore the scores and
play normally.
Iishanten peak theory
When thinking what the next draw will be, being likely to draw manzu because it’s cheap in
opponents’ discards is theoretically correct, but having drawn one, thinking that we’ll draw another
manzu because we have the “manzu momentum”, or on the contrary that we’ll draw a pinzu or
souzu to “even out” is a grave error. The same can be said not just of suits, but of numbers,
sequences and pairs.
The probability of advancing the shanten with a single tsumo p is
p =
tile acceptance tiles left in the wall
tiles left in the wall
with the average number of draws to advance being 1/p. Accordingly, the marginal value of
tile acceptance increases the lower tile acceptance is.
That’s why, from the point of view of isolated tiles, play to maximize the tile acceptance
when they form joints, and from the point of view of joints, play to make the bad shapes
complete more easily. In general, play to maximize future tile acceptance rather than
immediate tile acceptance, because there are less eective tiles closer to tenpai.
1
Fundamental rule of tile eciency
Play to maximize future tile acceptance closer to tenpai rather than immediate tile acceptance.
Example wti cut w or i
Cutting t gives the biggest tile acceptance right now, but it’s the easiest tile to make a good
shape with.
Example qqkllccv cut c
Example With >5 blocks, break the weakest block completely.
The advantage of winning rst
Mahjong is a game about scoring the most points. There are generally two strategies for this type of
games, namely scoring points and preventing opponents from scoring points. In mahjong,
1
TN: This one of the reasons why I don’t recommend the Euophrys eciency trainer.
12 CHAPTER 1. TILE EFFICIENCY
both are a factor, but the methods of preventing opponents form scoring points are limited. We
can not deal in, but this doesn’t prevent opponents from self-drawing or dealing into each other.
There is only one way to prevent those, namely by winning rst. In mahjong, scoring a win
directly prevents opponents from scoring and even lowers their score. Folding completely (betaori)
is generally not that good when we are close to winning ourselves. Therefore (and we draw a clear
line from what is commonly called tile eciency by the public), it is indispensable to learn tile
eciency to a high degree of precision.
1.1 Tile logic
Discard choice method
To win, we need four groups and one head (pair) (we do not consider chiitoitsu, kokushi musou,
nagashi mangan). To eciently create four groups and a head, it’s good to divide the hand into
groups and group candidates.
Classication of hand components
From most to least complete:
(1) Groups (面子, mentsu)
Sequences (順子, shuntsu): qwe
e
rt
Sets (刻子, kōtsu): kkk5
5
5
(Kans) (槓子, kantsu)
(2) (Simple) joints
2
(搭子, tātsu): become a group in one move
Penchan (辺張): qw
Kanchan (): ad, sf become ryanmen with one tile type and are called outer
kanchan, dg, fhbecome ryanmen with two tile types and are called inner kanchan.
2
TN: I have chosen to use this term instead of “protoruns” like Daina Chiba for the following reasons:
It’s much shorter (1 syllable versus 3).
They consist of two or more tiles joined together.
(Complex) joints can be used to form sets, not just runs/sequences as “protorun” would suggest.
It ts into the metaphor of a mahjong hand as a body with four limbs and a head. A joint is necessary to
form a limb.
1.1. TILE LOGIC 13
Ryanmen (両面) xc
The ryanmen is commonly called good shape, the other two bad shape.
(3) Pairs (刻子, toitsu) rr11
One of these is necessary to form the head. With two and up, they can be considered joints for
sets.
(4) Isolated tiles (oating tiles) Single tiles which can become a joint in one move and a group
in two. Includes shapes like wert or rtty that combine a group with a oating tile,
which we’ll discuss later. In general, we don’t include these under the term group candidates.
(5) Complex joints A type of joints, consisting of a joint and a oating tile, such as qqw
(penchan pair), qee(kanchan pair), eer(ryanmen pair), etu(ryankanchan), eeerrt
(a type of ryanmen pair). We’ll discuss their many possible types in detail later.
(6) Complex groups (many-sided waits) These are actually a type of joints. We use this name
to refer to complex clusters of tiles where the division into groups, joints, pairs and single tiles is
ambiguous. Examples are dfghj or dddf. However, if there is already another pair,
the latter will usually be considered a set and a single f. We will analyze this shape later.
Block theory
Groups, group candidates and the head are generally referred to as blocks. In mahjong, we must
create 5 blocks. If we have 4 groups or group candidates, the candidates are sucient, if we have
3 or less, they are insucient. If more than 5 exist in the hand, we have too much (overrun).
There may be multiple ways to divide a hand into blocks. For example, we can analyze qe
tuo as qe + tuo or as qet + uo. The analysis of a tile cluster can depend on
the rest of the hand. For example ddgj is dd + gj or ddg + j or dgj + d
if we have another pair, but if dd is our only pair, only the rst analysis is valid.
However, reading xvbn as xv + bn instead of x + vbn, or zxcvb as
zx + cvb instead of zxc + vb, decomposing complete groups or expressly analyzing
the joint as weaker is not done.
3
Discard choice patterns
With the components of the hand falling into the framework described above, we can divide possible
moves as follows:
3
Unless counting fu.
14 CHAPTER 1. TILE EFFICIENCY
1. Cutting an isolated tile
2. Cutting 1 tile from a complex joint
3. Dropping a joint or pair
4. Dropping a group
We will usually have to decide between 1, 2 and 3. When deciding between moves of the same
class, we can construct an order of precedence of shapes and choose the best shape, unless there is
some connection to yaku or dora.
For comparison between dierent classes, or identically good shapes, or when several possible
ways to break up a complex shape exist, we’ll have to establish dierent criteria.
In this strategy guide, we hope to create an all-encompassing classication of comparison criteria
to enable us to nd the best move.
Isolated tiles and simple joints
In mahjong, we must discard the tile we think is least useful every turn. We will now investigate
the basic order of precedence of isolated tiles and joints. We will operate under the assumption
that we don’t want to call and don’t care about the hand value.
To reiterate: we dene as n-shanten
4
a hand which requires n draws to achieve tenpai. Including
chiitoitsu, n is always at most 6.
5
For a group shape, n is at most 8.
6
Since achieving tenpai is a
prerequisite for winning, and achieving 1-shanten is a prerequisite for tenpai and so on, we will as
a general rule play the move that reduces shanten.
There are in general 3 kinds of moves that reduce shanten (for a group hand):
1. Making a joint from an isolated tile
2. Making a group from a joint
3. Making the head from an isolated tile
On the contrary, there are 3 kinds of moves that increase shanten (shanten return):
1. Dropping a joint with insucient group candidates
2. Dropping a group (except for cutting w from qqwe in an otherwise headless hand)
3. Dropping the only pair
While 1 is sometimes ecient to replace a weak joint with a better one, 2 and 3 are generally
inecient and constitute a loss. Because a head is easier to create than a group, 3 is more common
than 2.
From the above, the combined order of precedence for hand composition is isolated tile <<
joint <<< only pair <<< group.
Note on inequality signs:
4
The values of n are pronounced ii, ryan, san, suu etc. In practice, shanten counts below 3 are rarely used.
5
Where n = 6 - #pairs
6
Where n = 8 - 2×#groups - (1 if there is a head) - min(4, #joints, not counting the head)
1.1. TILE LOGIC 15
<<< almost always worse than
<< generally worse than, with the converse being true in limited exceptions
< a dierence exists, but it’s subtle; there will be many cases
where the rest of the hand or the discard piles will lead to the converse
Comparison of isolated tiles
Guest wind < 1·9 << 2·8 << 3 to 7 <<< 3445 or 3456
Taking the aka dora into account, 3·7 < 4·5·6, since 4 and 6 can make an aka ryanmen, while
5 always makes an inner kanchan.
When considering calls and yaku, a yakuhai pair is better than ryanmen. Isolated terminals
can’t make a ryanmen, but 2 and 8 can, and more easily than a yakuhai pair can be made from
a single yakuhai. Therefore in general, 1·9 < isolated yakuhai < 2·8, but this depends on the
rest of the hand (with many bad shapes, the value of yakuhai rises).
Comparison of simple joints
Penchan << outer kanchan << inner kanchan <<< ryanmen.
Taking the aka dora into account, 35·57 < 46, 13·79 < 24·68. But waits closer to the outside
are easier to win on, so with no aka the ranking is reversed.
Taking the aka dora into account, 23·78 < 45·56 < 34·67. Without aka dora, 45·56 < 34·67
< 23·78.
Inner kanchan and ryanmen contain middle tiles and are clearly better than isolated middles. A
penchan is similarly clearly better than an isolated 2·8, but the comparison between penchan and
isolated middle tiles is not so clear. In general, 3 to 7 < penchan. (In theory, an isolated middle
tile will create a group faster than a penchan given at least 12 draws, but even in the very early
game we should prefer the low shanten number allowing us to pressure opponents. However, this
can change with discards or through the inuence of other shapes.)
Comparing pairs and bad shape joints
Since at least one pair is required to win, we only have to compare pairs with other components
when we have at least two.
Two pairs
The tile acceptance is 2 types, 4 tiles, so similar to a bad shape joint. Let’s call honors and terminals
A-class pairs, 2s and 8s B-class pairs, middle tiles C-class pairs. These classes have respectively 0,
1 and 2 upgrades to a ryanmen, so the total amount of upgrades is equal to the sum of the parts.
Furthermore, when such an upgrade occurs, the resulting shape is a ryanmen pair, which is stronger
than a simple ryanmen. There are also upgrades into kanchan or penchan pairs. With 1 pair, these
upgrades can’t occur.
Accordingly, the order of preference is penchan < 2×A < outer kanchan < A and B <
inner kanchan < 2×B = A and C < B and C < 2×C. Often, preserving the two pair
shape is good.
16 CHAPTER 1. TILE EFFICIENCY
Three pairs
When dropping one of the 3 pairs, the loss is only 1 type, 2 tiles, which is less than a penchan.
Even an isolated middle tile is better. But because it has more upgrades than a bad shape joint,
a 3rd pair is better than a bad shape with only 2 tiles left. When deciding which pair to break,
choose the one that has been discarded the most and is dicult to turn into a set. If there is no
dierence, retain the ones with the best upgrades. (The case where the pairs are part of a complex
shape will be discussed later.) Often, breaking up the three pair shape is good.
Four pairs
The tile acceptance is low, but because it’s 2-shanten for chiitoitsu, break up bad shape joints
rst, especially when the group shanten is high and there are many bad shapes. When going for
a group hand, the order of preference is similar to the 3 pair case. With 5 pairs, we usually go for
chiitoitsu.
7
Complex joints I
Basic complex joints
Penchan pair qqw qww
Kanchan pair ssf sff
Ryanmen pair ccv cvv
Ryankan dgj
Of these, only the ryanmen pair is called good shape, the rest are bad shapes.
Comparison of basic complex joints
All of them except ryankan include a pair, so if the hand doesn’t have another head, they don’t
work as joints.
However, even if we have no other head and a shape like wwe, we can easily get a head
elsewhere, so the e is much stronger than a regular isolated e. It has a ryanmen upgrade on
drawing a pair into any other bad shape joint, so it’s about as strong as a cvvbor cvbn
serial shape. However, a shape like wwr is not as good, since it only has extra upgrades into a
7
These techniques stand in clear contrast to occult players like Tsuchida Kōshō, who often make conscious plays
for chiitoitsu from 3 or even 2 pairs. This should under no circumstance be attempted by beginner and intermediate
players who have not yet had time to develop their sense of ow.
1.1. TILE LOGIC 17
bad shape joint. When we draw e, we can make the good shape wwer which can be seen as
either a group or a pair + joint, so it’s slightly better than a lone r.
A complex bad shape has a tile acceptance of 8 tiles (including another pair for the pair shapes),
which is the same as a simple ryanmen. However, if it remains at tenpai, it has to be broken down
into a simple bad shape, and is therefore weaker.
The order of precedence of complex joints of the same type is similar to that of simple joints,
with more central joints being better because they have more upgrades. When comparing wwr
with sff, the dierence is small and the rest of the hand plays a large role. When deciding
what to cut from wwrr, when we draw t, we get either wwrt or rrt. So when we
want to create just a group, we cut w, but when we want a group and a pair, we cut r.
When comparing complex joints, we don’t want to get rid of them entirely like when comparing
simple joints or isolated tiles, but drop one tile and turn them into a simple joint. To get the
optimal wait in the end, drop one tile from the strongest shape as a general rule.
However, when breaking up a complex joint that contains a pair, there are situations where we
want to x into a simple joint, and situations where we want to x a pair. We will discuss the
dierence below.
With two pairs
Fix the bad shape into the head. With two ryanmen pairs, turn one of them into the head,
depending on dora, yaku, discards etc.
With three pairs
One complex joint Drop the pair from the complex joint.
Two complex joints If we have a ryanmen pair, x the ryanmen. If both the complex
joints are bad, x the one with the most ryanmen upgrades as a general rule. However,
in qqwhhm.., the simple pair has good upgrades, while the complex joints do not,
so temporarily cut w, hoping to draw gj. This is even more applicable if the simple pair is
connected like dfghh.
Three complex joints If all the complex shapes are bad, x the worst one into the head.
This gives a momentary loss of 2 tiles of tile acceptance, but creates a better shape later on once
one of the joints completes into a group.
With one ryanmen pair, x the ryanmen. With two ryanmen pairs, x the bad shape into
the head. With three ryanmen pairs, there is no big dierence, so consider the usual suspects of
discards and dora.
With ryankan and ryanmen pairs, x the ryanmen. With two ryankan, try to x one towards
accepting an aka dora, cutting w from wry, leaving the upgrade into ryanmen with u.
Otherwise, try to create a suji trap by cutting g from adg.
18 CHAPTER 1. TILE EFFICIENCY
The comparison between ryankan and paired bad shapes is dicult. With a three pair shape,
x the strongest kanchan, hoping to draw a ryanmen upgrade. If already iishanten, the upgrade
is less important and we can x the ryankan into a desirable kanchan as above.
Complex joints II
When comparing complex joints, the presence of connected groups or pairs can create extensions.
An extension is stronger than the original shape, but cutting a tile from the extension leads to
a bigger loss. We therefore want to keep extensions alive as much as possible, an exception to
the principle of xing strong shapes. There are many kinds of complex joint extensions, with the
following being the chiefest.
Penchan pair extensions
aassdf aaassd
Kanchan pair extensions
ssfghj sffghj dghjkk
adddfg dddfgg
Ryanmen pair extensions
sdfggh ddfggh dfgghh
dfgggh fggghh
Ryankan extensions
8
sfghjl(long ryankan)
sfghhj(ryanmen kanchan)
ssfhh(ryankan pair)
aadfghkk(long ryankan pair)
sddfghjjk(double ryanmen kanchan)
8
These are really important and you should denitely memorize these, especially the rst three.
1.1. TILE LOGIC 19
Using complex joint extensions
Like the ryanmen kanchan, complex joints can be dicult to notice if you’re not used to them,
so it’s important to pay close attention. The ryanmen kanchan has the same tile acceptance as a
ryanmen pair, but is guaranteed to produce a sequence, so we should prefer it over a ryanmen pair
in a pinfu hand.
Bad shape extensions tend to have many upgrades into a good shape. We therefore want to
preserve them. In a two pair shape, we x the regular complex joint into the head, keeping the
extended shape. In a three pair shape, we drop the pair from the extension.
With complex joints that contain 3 identical tiles, the ryankan pair and the double ryanmen
kanchan, the loss from breaking them up is especially big, so we prefer to keep them. With multiple
such shapes, we drop 1 tile from the one most likely to give a good shape.
Example ertttyaadggm,. cut t
In a three pair shape, the choice between xing ertttyinto a good shape and dropping
a tile from a complex bad shape is dicult. If the bad shape is an inner kanchan, we x it and
hope for ryanmen upgrades. Otherwise, we x the ryanmen.
Example ertttyaadllbmm cut m
Example ertttyaadllm.. cut t
Adding to the loss that comes with breaking up extensions, they can easily progress into better
extended shapes by drawing more tiles.
Example eerrtyyujklmm, cut m
However, memorizing all these dicult shapes takes a lot of time and isn’t really necessary. If
we remember that joints become stronger when they’re connected to groups or pairs, we can deal
with most hands correctly.
If possible, we should also try to remember the shapes that lead to the strongest extensions by
cutting one tile (aaddgg cut d) or by drawing one tile (adgg draw a). Especially
the latter are important because they are easy to overlook.
As a general rule, to create strong shapes, we also want to keep their precursors, and the
precursors of those precursors. This will later allow us to classify the relative strength of simple
joints and isolated tiles depending on their surroundings.
Ultra bad shape joints and furiten joints
So far we have not considered what tiles have been discarded yet. We will now discuss the most
important inuences of discarded tiles on tile eciency, namely depleted tiles and furiten.
Ultra bad joints (bad shape joints with 2 tiles or less left)
Since the marginal value of tile acceptance increases when it’s low, the dierence between 4 tiles
and 2 tiles is rather big. When in tenpai, it’s quite painful to have an ultra bad shape left (a head
start riichi in the mid game with such a wait will deal in more often than win). We prefer a 3rd
pair over such a joint. We also prefer an isolated middle tile (or even a 2 or 8 if the depleted joint
is a penchan), breaking the depleted joint and trying to build another.
20 CHAPTER 1. TILE EFFICIENCY
However, a bad shape joint with 3 tiles left is not that bad. Also, we prefer a ryanmen with 4
tiles left over a bad shape with the same amount of tiles left, since we know opponents don’t want
to use those tiles.
An extra pair of which the other two tiles have been discarded can be treated as a oating tile,
so it’s also not as bad as a depleted joint, especially if it’s a middle tile.
Unless 3 or 4 tiles of the same type have been cut, discards don’t really matter for comparing
isolated tiles, since the dierence in ease of creating a good shape between a 1, 2 and 3 is more
important.
We should also consider upgrades of bad shapes that have become depleted. For example, if h
has been cut 3 times, dg becomes dicult to turn into a ryanmen, and a ryankan with j is
also disappointing.
All these make it that remembering to look at the discards has a rather big impact on results.
Furiten joints
We can’t ron while in furiten. But this only matters in tenpai, and a furiten good shape has a win
rate not much lower than a regular bad shape. Accordingly, we should prefer furiten ryanmen over
bad shapes. Furiten bad shapes are bad, and we’d rather have an isolated tile. (Unless it’s already
the end game and we want to collect no-ten payments.) Similarly, an isolated tile that can make
a furiten joint is worse than one of the same class, but better than one of a lower class. When
choosing how to break up a complex joint for riichi, we usually pick the wait that isn’t furiten, even
if it’s narrower.
For example, cutting q from qw and drawing e, we should keep it and go break up a bad
shape (that’s why we usually break bad joints from the outside). Cutting q from qa and
drawing w or e, we keep it and cut a.
Comparing components of the same class
The interaction of tiles
Apart from neighboring tiles being heavily discarded or being furiten, isolated tiles and joints of the
same class can still be better of worse through the presence of other components (especially joints)
that have an overlap with them. This means that their tile acceptances or upgrades compete for
the same tiles, weakening them, or that they will compete for tiles once an upgrade occurs. For
example, in wt, the two isolated tiles compete for e and r.
We can also have combos, which are shapes that have the same tile acceptance as a regular joint
or isolated tile, but are easier to upgrade or have upgrades to a superior shape. For example, the
m in cvbm is stronger than a regular isolated m, because when we draw n, we get the
strong cvbnm shape.
There are also cases where an overlap and a combo exist at the same time. In general, if there’s
an overlap, the shape is weaker than usual even if a combo exists. A typical example is
a eryu shape which has an overlap on the t, but creates a strong combo once we draw it.
1.1. TILE LOGIC 21
An exception to this general rule are shapes where the overlap is for a bad shape-creating tile and
the resulting combo is a better shape than normal: for example, z and b both become stronger
than usual in a zb shape, since we can draw c for ryankan.
When comparing overlaps and combos, their quantity and quality are both important, but in
the case of an overlap and combo existing at the same time and weakening the shape, quantity >
quality since we want to draw the combo as soon as possible.
In general, we also prioritize overlaps and combos that exist right now, rather than those that
will be created when an upgrade occurs.
Diagram of component precedence
We can roughly summarize preference between components (joints and isolated tiles) of the same
type as follows:
Compare overlaps in the tile acceptance
Compare the strength of the shapes that are created when a tile is accepted
Compare overlaps in the upgrades
Compare combos with other components
Like this, we get the following order: overlap in tile acceptance < overlap in tile ac-
ceptance, but once the tile is accepted, the shape is stronger than normal < weak
overlap in tile acceptance < overlap in upgrades < overlap after an upgrade < normal
< combo after an upgrade < weak combo < strong combo.
A weak component of a class can be compared with a component of a lower class (weak 3 versus
2), a strong component with one of a higher class (strong outer kanchan versus inner kanchan).
By understanding what joints are weak and strong, we can understand what isolated tiles are
good or bad at making strong joints. We’ll therefore rst compare joints, and continue with isolated
tiles.
In the following sections, there are some points of attention to keep in mind.
We’ll assume that comparison of joints to joints takes place in an overrun situation (>4 joints),
that of isolated tiles to joints in a non-overrun situation. We’ll come back to overruns later.
When not stated otherwise, assume we have a head elsewhere in the hand.
There will be some shapes that give rise to iipeikou, put we will consider only eciency and
disregard the possible extra score.
As always, there are exceptions when overlaps and combos are dicult to analyze, but the above
should be a good guideline. Now, because this theory can be quite perplexing when put into words
abstractly, we’ll put in it into practice on the most common shapes.
22 CHAPTER 1. TILE EFFICIENCY
Penchan
Summary
qwwr< qwry< qwrr< qwrt< e< qwtt< qwty
< qwyy< qwyu< qw< qwtyu< qwrty< qqwwe
Tile acceptance overlap
qwwr
To make two groups here, we need to draw e twice, and we will commonly cut q to create a
wwr kanchan pair. The q is essentially useless, and we’ll cut it over an isolated a.
qwry
It’s easier than the above shape to make two groups, but still not desirable. By cutting q, we get
the ryankan wry. The q is not worth keeping over an isolated s, or even a unless the rest
of the hand is very bad.
qwrr
Similar to the above shape, but if we draw the e, the resulting qwerr is a bit stronger
than qwery, but because of the overlap (we can cut q, drawe and still end up with a
group + oating r), this shape is still weaker than just qw.
qwrt
Drawing e instantly, we get qwert group + ryanmen, which is a good shape. All of the
above penchan are inferior to an isolated d. In general, any bad shape joint with a tile acceptance
overlap is worse than a oating middle tile.
qwtt
No direct overlap, but if we drop the penchan and draw the e backre, we still get the kanchan
pair ett. The pair can also upgrade into the above shape.
Upgrade overlap
qwty
Only overlaps for upgrading the penchan into wr kanchan. Not a big dierence from a regular
1.1. TILE LOGIC 23
penchan.
qwyy
Compete for r to upgrade into wr and ryy.
Post-upgrade overlap
qwyu
When we draw r and upgrade, there is an overlap for the next upgrade with t.
We might even say that a qwui shape is worse than a normal qw, because we draw r,
then t and get overlapping ryanmen rtui... But that will almost never happen in practice.
In general, when tiles are separated by at least 5, we can safely ignore their inuence on each other.
Normal
qw
Upgrade combo
qwtyu
Drawing r, the wrtyu shape has many upgrades into ryanmen.
qwrty
Transforms into the above shape on drawing u.
However, because a penchan can’t upgrade into a ryanmen directly, at 1-shanten, we should cut
a from qwasfgh, since we can draw the backre d and make a furiten sanmenchan.
This is a penchan-only exception, and from wrsfghj we cut w.
Combo
qqwwe
Makes a complex joint when drawing any of qwr. (The qwwer shape can be considered
as qwe + wr and will be discussed under outer kanchan.)
We will often want to drop a penchan to keep a oating tile. The following shapes make this
especially eective:
24 CHAPTER 1. TILE EFFICIENCY
tio
Overlap for yto upgrade the penchan/complete a ryanmen, and for uto complete the group/com-
plete a kanchan.
rio
Overlap for y to make ryankan.
Outer kanchan
Summary
adfh< adff< aasf< addg< addf< adgh<
adhh< adhj< ad < adhjk< adgg(g is the only head)
< aasdd< addfg< assdf< ssdff< adghj
< adfgh
Tile acceptance overlap
adfh
The hardest shape to make two groups in, we often want to slim this down to just df and make
one group. We’ll still keep the a much more often than the q in qwwr.
adff
Similar to the above, but becomes a head + ryanmen pair if we draw another a.
aasf
Unlike the above, we can upgrade into a ryanmen by drawing g. In real matches, dropping the
aa and going for tanyao is common.
addg
Cut a for kanchan pair or d for ryankan, a similar idea to q from qwry.
addf
Instantly becomes good if we draw s. With all of the above, we’ll often cut one tile and prefer a
1.1. TILE LOGIC 25
oating middle tile, similar to penchan.
Upgrade overlap
adgh
Overlap for ryanmen upgrade and group completion.
Post-upgrade overlap
adhh
Kanchan pair with f.
adhj
Overlapping ryanmen with f.
Normal
ad
Upgrade combo
adhjk
Easy to upgrade ryankan with g.
Combo
adgg(g is the only pair)
Ryankan pair with a. If we have another head, worse than a regular zc, cutting a or g.
aasdd
Strong kanchan pair with ad, ryanmen pair with f.
addfg
Upgrades into a complex joint with any of adgh.
26 CHAPTER 1. TILE EFFICIENCY
assdf(penkanchan)
Upgrades into a complex joint with any of asfgh.
ssdff
Upgrades into a complex joint with any of asfgh, with better shape post-upgrade than the
last one.
adghj
Sanmenchan with f, ryankan not only with g but also with k. Still not as good as an inner
kanchan, which has 2 ryanmen upgrades.
adfgh
Upgrades with f for ryanmen, g for ryanmen kanchan, j for sanmenchan, k for long ryankan.
Clearly better than an inner kanchan.
Inner kanchan
Summary
cbnn < cbbm < cbbn < cbm, < cb < zxcvn <
xcvvn< xxcb(x is the only head) < ccvbb < cbnm,
Since an inner kanchan is just an outer kanchan with one more ryanmen upgrade, the explanation
has been omitted where similar to the previous section.
Tile acceptance overlap
cbnn cbbm cbbn
The dierence from the corresponding shapes with an outer kanchan is that these can become
ryanmen, so it’s common to keep these over a oating tile. Because they reduce tile acceptance, we
will often drop these for a penchan or outer kanchan. (But when a good end shape is important,
we’ll keep these.)
Upgrade overlap
cbm,
Normal
cb
1.1. TILE LOGIC 27
Combo
zxcvn
No extra ryanmen upgrades, but easier to make a paired joint.
xcvvn
Can draw v for good shape, so slightly better.
xxcb(x is the only head)
Ryanmen upgrade not just on xn, but also on b. Similarly, a xxcbm ryankan has an
extra ryanmen upgrade on m. In general, tiles next to the only head become better once a head
completes elsewhere in the hand.
ccvbb
Becomes a strong complex joint with c or b.
cbnm,
Very easy to upgrade into ryanmen.
Ryanmen
Summary
wwrtuui(with no other head) < errtyyu< rrtt< eryu
< eety(with no other head) < er< qwwee< qweer< wweerr
< qwert< weert < werty
Because a ryanmen is so strong, the advantage or disadvantage of overlaps and combos is rather
small. Accordingly, when comparing ryanmen, we should bear in mind that the importance of
discards relative to the hand shape increases.
Tile acceptance overlap
wwrtuui(with no other head)
An extremely unusual shape, since cutting t causes no loss in tile acceptance.
errtyyu
By cutting r or y, this overlapping ryanmen shape becomes a sanmenchan.
28 CHAPTER 1. TILE EFFICIENCY
rrtt(double ryanmen)
Double overlap on ey. Cutting one tile gives a ryanmen pair.
Even with a bad overlap like this, the nal wait when in tenpai will be good, so we prefer this
kind of shapes over simple bad shape joints. Still, we prefer a ryankan over this shape.
eryu
Overlap on t. Drop this over another ryanmen.
eety(no other head)
Cutting y is still salvageable when we draw r.
Normal
er
Combo
qwwee
Drawing w or e, we get a complex joint that waits on qwer, but in practice it’s harder to
draw on vertically than a normal ryanmen.
The following are variations of the same shape that are somewhat easier to draw:
qweer
wweer
qwert
weert
Can make a ryanmen kanchan with u.
werty(sanmenchan)
The strongest possible 5-tile shape.
1.1. TILE LOGIC 29
Pair dropping
We have touched on this topic in the section on comparing pairs and bad shape joints, but we can
also compare pairs to each other.
Pair dropping process
We usually think of dropping a pair when we have at least 2, and we have seen earlier that in a
hand with exactly 2, dropping a bad shape joint instead is common.
However, in a hand with few groups and ryanmen and many bad shape joints, there are cases
when dropping one of the 2 pairs is preferable over dropping a joint. The reason is that in a
high-shanten 2-pair hand, the probability of drawing a 3rd pair before tenpai is high, creating
an undesirable 3-pair shape, which we would try to break by cutting a pair from a paired joint.
Therefore, instead of waiting for that to happen, we drop a terminal pair in advance, hoping to
create a superior 2-pair shape later on, following the theory of emphasizing tile acceptance closer
to tenpai over immediate tile acceptance.
Example weyiaaf;kkxvn,dora k
instead of slimming down souzu, drop a and start forcing tanyao
With 3 pairs, we usually want to break a pair and return to a 2 pair shape. However, if we’re
certain the future 2 pair shape will be suciently good and don’t need any further improvements,
we can preserve the 3rd pair to maximize tile acceptance right now.
Example wweuddfhjkcv22 condently cut u
9
In 3-pair hands, if we have ying pairs like wwrr or kkll, we should preferentially
cut 1 tile from these, to preserve the horizontal tile acceptance. However, if we have at least 4 pairs,
we should preserve this shape since it’s a many-sided wait and can gives us iipeikou. Whether to
cut the inside tile or the outside tile from this kind of shapes has been discussed earlier: if we are
content with a group, cut the outside; if we need a group + a pair, cut the inside.
If we don’t have any ying pairs, we should break the pair that has the weakest upgrades into a
joint, so usually the most outside pair, comparing the pairs the same way we compare isolated tiles.
However, from qqttaa, we should denitely cut a, since we can draw e for a ryankan
pair. We will discuss the relative worth of isolated tiles next.
Ukase-uchi
Up until now, we have discussed dropping the most unneeded pair from the hand entirely. There’s
another kind of pair dropping, where we cut only one tile from a (preferably middle) pair, down-
grading it into a oating tile and hoping to stick tiles to it horizontally. This is a special move
called ukase-uchi. We use it when we want to upgrade to a sticky shape, or when the remaining
joints are all too weak to make a decent hand. We can also use it when we have sucient ryanmen
joints, to create yaku, or in shapes like qquommm,. (1 q left) where a shanpon wait
would be extremely painful.
9
These examples were not present in the original, I added them to illustrate the idea more clearly.
30 CHAPTER 1. TILE EFFICIENCY
Isolated 1 and 9
We can compare isolated tiles using the same method we used to compare joints, considering overlaps
and combos. However, because there many more possibilities to draw up to a group, there will often
be many possible overlaps and combos in dierent future shapes, making comparison more dicult.
It will be good to consider these sections more as a general outline that can be complemented by
information from discards and desired yaku.
Summary
qru < qrr < qr < qry < isolated guest wind < qrt < qwr
< qwwr< qtu< qty < q< qer< qqwe< qtyu <
qrty< qrtty< qt< qery< w< qeryi< qert
Tile acceptance overlap
qru
Even after we draw ty for qrtyu, there’s still overlap between q and r, so q is
unnecessary.
qrr
Can make a complex joint wrr or err, so weaker than just qr. Even if rr is the
only head and we can try to make a group with the q, it’s still clearly weaker than a normal q.
qr
The famous shape with an overlap for we. Even though we can draw towards qwer, a
good wait in a headless shape, it’s still clearly weak.
qry
Ryankan on w, ryanmen + oating tile on e. The loss from missing out on qery doesn’t
really hurt.
With all of the above, we prefer to keep an isolated guest wind because of its defensive power
(especially if we can draw a pair).
qrt
Drawing w or e creates an overlapping shape. But the loss from missing out on a qert is
1.1. TILE LOGIC 31
quite big.
qwr
Overlap on both w and e, but can draw the qwer serial shape, which is better than the
above, especially when we have no head.
qwwr
As discussed earlier, it’s usual to see this as q+ wwr. But we can miss out on the qwwer
shape which is slightly better than the above.
qtu
Only overlaps on e for ryankan, which makes it better than all of the above.
Post-upgrade overlap
qty
After drawing e, qety has an overlap for r.
Normal
q
Combo
qer
Has many possible overlaps and combos, so dicult to compare. When there is no head, the
qwer shape is valuable, so in that case it’s somewhat better than a lone q.
qqwe(aryanmen)
10
Group + head with q or r, connected shape with w or e.
qtyu
The kanchan with e has better upgrades than normal.
10
Do not confuse with the Aryan Men local yakuman (qriiafkkzv,,55)
32 CHAPTER 1. TILE EFFICIENCY
qrty
As above but better.
qrtty
Can draw e for ryanmen kanchan.
From here on, if aiming for a closed hand, it’s common to to keep these over a single yakuhai.
qt
Makes a ryankan with e. In the above shape, cutting q and drawing e still gives a ryanmen,
while here we get a simple kanchan which is a bigger loss.
qery
It’s usual to see this as q + er + y, but drawing t creates a strong qerty kanchan.
From here on, the value is higher than an isolated 2.
qeryi
Can make a ryankan (quasi-good shape) with w or t, while a lone s can only make a ryanmen
with d.
qert
Ryanmen with w, strong kanchan with y, clearly better than a lone s.
(we’ll analyze the qwer shape as qwe + r in a later section.)
Isolated 2 and 8
Summary
sfg < sgj < sfgj < sgg < sgk < sg < shk <
sgjl< shj< s< sfgjl< shjk< sghj< sghhj
< sfgh< ssdf < sh< d
1.1. TILE LOGIC 33
Tile acceptance overlap
sfg
Overlap on d, but we can miss out on sdfg.
sgj
Overlap on d and f, but we can miss out on the sd ryanmen, so stronger than the above.
sfgj
Similar to qery.
sgg
Similar to sg, but weakens the s since the kanchan pair dgg is stronger.
sgk
Same logic as qru<qr. But because it can make a ryanmen, it’s better than the q in
qt.
sg
Overlap on d and f.
All of the above are usually considered weaker than an isolated yakuhai.
shk
Overlap on f, but not on d.
sgjl
Appears to have an overlap, but the sfgjl shape is not that bad.
Post-upgrade overlap
shj
After drawing f, has an overlap on g.
34 CHAPTER 1. TILE EFFICIENCY
Normal
s
Combo
sfgjl
Same as qeryi.
shjk
Can draw f for sfhjk, which gives a sanmenchan with g and ryankan with l.
sghj
Strengthens the kanchan with f.
sghhj
Ryanmen kanchan with f.
sfgh
Sanmenchan with d, strong kanchan with j. Still not as good as a middle tile with 2 upgrades
into ryanmen.
ssdf
Easy to connect shape. Much stronger than a qqwe shape. While sfgh makes it easy
to create a kanchan, this one makes it easy to create a pair. Depending on what we want (how
much pairs we already have), either can be better.
sh
Ryankan with f. Still not as good as a middle tile.
Isolated 3 to 7
Summary
xcbm,< x< cbn< cn,< ccn< zzv< cn< cmm
1.1. TILE LOGIC 35
< cm. < cm,< c< zxcc< cnm,< cnmm,< zxcv
< cm< xcvv< cbnm< ccvb< penchan < cvvb< xcvb
< cvbn< ccvbnn(no other head) < zxcvbnm< xcvbnm,
Tile acceptance overlap
xcbm,
Has an overlap on both sides. Pretty much the only case where a middle tile is worse than a 2.
cbn
Overlap on the v, but misses out on the cvbn shape.
cn,
Overlap on v for ryankan and b for ryanmen upgrade.
ccn
Overlap on the v and b for a complex joint.
zzv
As above, but the possible complex joints are not as good.
cn
Overlap for simple joints, so not as bad as ccn.
cmm
Overlap on b for kanchan pair.
cm.
Overlap on b for ryankan.
Post-upgrade overlap
cm,
Similar to qty.
36 CHAPTER 1. TILE EFFICIENCY
Normal
c
Combo
zxcc
Easy to make a serial shape.
cnm,
Strong kanchan with b.
cnmm,
Ryanmen kanchan with b.
zxcv
Serial shape.
cm
Ryankan with b.
xcvv
Easy to make a serial shape.
cbnm
Sanmenchan with v, strong kanchan with ,.
ccvb
Easy to make a serial shape, more likely to give good shape than xcvv.
The patterns from here on make it extremely easy to create good shapes, and are much
stronger than any other oating tiles. They are often better than a penchan, and comparable
to an outer kanchan.
1.1. TILE LOGIC 37
cvvb(nakabukure)
Ryanmen with any of xcbn.
xcvb(connect 4 shape)
Ryanmen with zcv, sanmenchan with n, strong kanchan with ,.
cvbn(connect 4 shape)
Even better than xcvb, makes sanmenchan on xm.
ccvbnn(no other head)
Makes a ryanmen with any of xvbm and is easy to extend further.
zxcvbnm(connect 7 shape)
Ryanmen with vb, sanmenchan with c, and can give ittsuu. We will often cut a tile from
ryankan or a kanchan pair to try and extend this shape.
xcvbnm,(connect 7 shape)
Ryanmen with cm, sanmenchan with zvn. and can give ittsuu. The best possible oating
tile.
Joint dropping
So far, we have discussed that there are four possible discard choices in a mahjong hand:
1. Cutting an isolated tile
2. Cutting 1 tile from a complex joint
3. Dropping a joint or pair
4. Dropping a group
Of these, dropping a group is a special move that only makes sense when chasing value, so we
will not discuss it here. We have already considered comparisons between moves of the same type,
as well as (in part) comparisons between 2 and 3. From now on, we will discuss comparisons be
that fall into the remaining cases.
When deciding to drop a simple joint, we do not only have to decide which joint to drop, but
which of its tiles to cut rst. We will now examine this question.
38 CHAPTER 1. TILE EFFICIENCY
Joint dropping process
It’s often easy to decide what tile to cut rst when dropping a joint. When we don’t have enough
group candidates, we want to keep the tile that has a chance of making a good joint while isolated.
That’s why we usually cut joints from the outside in. When we have sucient group candidates,
we can also consider the added value from yaku or dora that the tile we keep allows us to create.
Finally, there’s the defensive value of the remaining tile. In general, outside of mid -late games
where the end is in sight, upgrades are more important than defensive power.
There are some dicult situations where cutting a tile while leave a complex joint, and there
are several dierent complex joints we can choose to retain.
The example of wwrr has already been discussed.
From eetu, we can make a ryankan or kanchan pair. If completing the ryankan would
give us pinfu, we should prefer it. Otherwise, we’ll choose the shape with the most upgrades into
ryanmen. If we are able to call, we should keep the kanchan pair to call pon.
Even in pinfu shapes like qweuiddfghccbm, we should take the kanchan
pair if the head has many upgrades into a ryanmen.
Problem wrrtyyu cut w or r?
In a pinfu shape, cut r, else cut w to make iipeikou. When calling, cut w. (With tanyao
pinfu cutting wis not bad.) From wrtyyyu and wrtyyuu, we clearly cut w.
qetu wryi(sankanchan)
qetuo(suukanchan)
These shapes are not that dicult, but can turn into more complex shapes like qeetu
(sankanchan pair).
Though we can analyze them as complex joints, as a whole they form exceptional shapes that
we have not analyzed yet. (Cutting a tile from in a non-overrun increases the shanten.) Let’s try
to compare their strength to other types of components.
A sankanchan has no overlaps, but if we cut one tile from it we end up with a ryankan, so
it’s easier to break up than an outer kanchan. A qetu shape can upgrade into a ryanmen
with i, and we prefer it over an isolated middle tile, but cutting a tile from wryi to keep a
oating tile can be done. A suukanchan is stronger than a sankanchan, about on the same level as
an outer kanchan, but worse than an inner kanchan.
1.1. TILE LOGIC 39
Sankanchan and suukanchan pairs
The author considers this not as important and refers to the following blog post (日本語): https:
//chirno.hatenadiary.org/entries/2008/05/18
11
Comparing simple and complex joints
The general rule of tile eciency is to maximize tile acceptance close to tenpai. Often,
cutting a tile from a complex joint will maximize the immediate tile acceptance, but narrow the
shape down the road. Accordingly, in an overrun (>4 joints), we should break a simple joint
completely. Obviously, we should pick the weakest one. We should not ignore the possible benets
of leaving one tile (the surplus tile) when deciding which of the tiles to cut rst.
There are the following exceptions:
The complex joint is lower class than the weakest simple joint
For example, when we have the simple joints are all ryanmen and we have a kanchan pair. Since
we want to keep the ryanmen, we should cut a tile from the complex joint, in such a way that if
it completes, we get the most desirable result. (For example, cutting o from ioo.) But in a
hand like qqettdfxccvbm,, we cut ,.
12
The shape we get when the weakest joint completes is very strong
Because it gives us yaku or dora. With yaku, we can often cover the loss in speed by calling.
Example ioghjklzzxm,55 cut x
In an overrun, we will often compare simple joints with oating tiles. Since dropping a joint
doesn’t reduce shanten, we will often want to keep a good oating tile instead of a joint. (Whether
to keep a safe tile over a joint is dicult.)
For example, we’ll keep a oating middle tile over a penchan, and a serial shape over an inner
kanchan. We will sometimes even drop ryanmen to keep dora or create yaku. In a headless overrun,
we’ll often drop bad shape joints over aryanmen like uioo and not care too much about the
head.
Example qeradghcvbb111dora q cut a
Example weuioosdjlxcvb cut l
At iishanten, whether to take the straightforward shape or to drop a joint and try to get a better
wait from a oating tile is dicult.
11
In general, these are slightly better than a regular shape but not by much. For example zccbm33
accepts 1 more tile type than zccgj33, and zccbmm. accepts another 1 type more.
12
This is an exception to the exception, I don’t know why the author chose to include it. It’s the correct move
because the ryankan pair on manzu is strong, we can cover n with a ryanmen kanchan, and we preserve 345
sanshoku.
40 CHAPTER 1. TILE EFFICIENCY
Example qetyaaszcbnm222dora b cut sor qw
Example qqetyjkxvnmm,. dora r cut e
We have enough ryanmen, so the advantage of drawing w is small.
In an overrun, we prefer to cut 1 tile from a joint in such a way that the surplus tile forms a
complex joint, like from qeet. But we still want to emphasize tile acceptance close to tenpai:
Example tysdghzccb,.44 drop ,.
Comparing isolated tiles and complex joints
Cutting a tile from a complex joint and keeping a oating tiles with insucient group candidates
makes the joint a bit more dicult to complete, but makes it possible to create another group
candidate with the oating tile, increasing the win rate. It is nearly always limited to xing a
ryanmen pair into a ryanmen, or a bad shape paired joint into the head (other cases are more often
than not inecient).
Since it’s usually more dicult to make a group from a joint than joint from an isolated tile, we
only do this when the loss from the oating tile is very big. Also, a ryanmen pair can often end up
as two groups. (Especially drawing t into err is very big.) With wwe, it’s easier to form
two groups than with an isolated w, but an isolated e is still preferable. With eer and up,
the loss in eciency is big, and it’s good to keep the extra tile over isolated tiles. In shapes like
vv/ or xccvbn, the gain from completing a set is smaller and we will often slim down
these shapes to keep oating tiles.
Example wweoocmm,.gghj cut w
There are also situations to x the head. When xing a ryanmen turns a bad shape paired
joint into a head + oating tile, we can consider if it isn’t easier to create another group elsewhere
(wwejll cut w, errkll cut k).
When we have a oating tile in a nakabukure or connect 4 shape, we’ll often x a ryanmen to
preserve it. Still, we’ll often preserve a bad shape complex joint. We’ll only cut from one when it
moves us towards yaku (uoosdfgkkcvnm, cut o) or to preserve a connect
7 shape.
These decisions will change a lot depending on yaku and dora, so we’ll want to give special
thought to those in later chapters.
Complex groups (many-sided waits)
Using complex groups
A shape like errr can be used a 3-sided wait if it contains the head, but if we already have
a head, it’s more likely to be seen as rrr and a weakened e that is more dicult to make a
sequence with.
1.1. TILE LOGIC 41
With this shape, we can have the decision at iishanten whether to take the irregular wait or
to take a very wide headless iishanten. We will return to this topic in the chapter on iishanten
eciency.
It’s not really necessary to think about the relative desirability of complex groups, but it can
be dicult to see what the actual wait is. Dicult waits come up rarely, but being able to solve
them quickly is directly tied to good results.
13
Classication of waits
1 tile 3 waiting on 3tanki
4 tiles
With 0 sets
qw33waiting on epenchan
wr33waiting on ekanchan
ww33waiting on w3shanpon
wertwaiting on wtnobetan
erttwaiting on wtaryanmen
we33waiting on qrryanmen
With 1 set
qqqwwaiting on wepenchan tanki
qwwwwaiting on qepenchan tanki
etttwaiting on erkanchan tanki
rtttwaiting on eryryanmen tanki
7 tiles
With 0 sets
13
When not playing with tips like a middle schooler :^)
42 CHAPTER 1. TILE EFFICIENCY
qwertyuwaiting on qrusanmentan
qwerrtywaiting on qru
werty33waiting on qrusanmenchan/piano wait
With 1 set
weeertywaiting on qwru
eeerrtywaiting on wrtu
eeerttywaiting on rtu
eeertyuwaiting on wrtuithe famous 5-sided wait
eeertyiwaiting on ui
eeettyuwaiting on rti
eeetyuiwaiting on rti
eerrrttwaiting on ert
eeerrttwaiting on erty
eeert33waiting on ey3entotsu/chimney wait
With 2 sets
wwwerrrwaiting on qwerttatsumaki/sandwich wait
wwweeerwaiting on wertopen sandwich wait
wwwryyywaiting on ert
Using 4 tiles
eerttttwaiting on ery
wweeeerwaiting on qwrt
1.1. TILE LOGIC 43
weeeertwaiting on qwrt
10 tiles
eerrttyyuuwaiting on eryu
eeertyuuiiwaiting on yuio
eeertyyuiiwaiting on tui
eeertttyuuwaiting on tyu
eeerrrttuuwaiting on wtu
eerrrttyuuwaiting on wty
eeerrtttyywaiting on rtyu
eeertyuiiiwaiting on wertyuio
eeerttyuuuwaiting on ertyu
eeertyuuuiwaiting on eyuio
And as a bonus, here are some 13 tile shapes that wait on any tile in a suit:
weeeertyuuuui
werrrrtyyyyui
wwwertyyuuuui
qqqwertyyyyui
wwwertyuuuuio
qqqwertyuiooo
Solving many-sided waits
Tha author refers to very a long blog post by someone else at http://ameblo.jp/010101/entry-10514689527.
html. The best way is of course to practice, for example with https://www.gamedesign.jp/flash/
bamboo/bamboo.html, the chinitsu problem book by Baba Hirokazu or actual tiles.
In the following chapters, we will discuss
Eciency taking into account score and calls
44 CHAPTER 1. TILE EFFICIENCY
Riichi and calling judgment, to understand the balance between score and speed
Details of yaku and dora usage, ditto
What tiles to keep for calling and yaku, how to choose discards with the above knowledge
Iishanten eciency
1.2 Head start tenpai judgment
Understanding tenpai eciency
This isn’t really tile eciency, but we’ll take a look at whether to take head start tenpai. (Head
start means we are the rst player to tenpai.)
The reasons for including this in the tile eciency section:
By understanding the strength of head start tenpai (riichi), we can recognize the importance
of tile eciency to make fast tenpai.
By understanding in what situation to take head start tenpai, we can understand what moves
we need to make to make this possible, which is not the same as maximizing tile acceptance.
(Tile acceptance that leads to a tenpai which it’s better not to take can’t be considered tile
acceptance.)
By understanding what tenpai is strong (cheap good shape versus expensive bad shape etc.),
we can understand how to balance speed and value in tile eciency before tenpai.
Head start riichi judgment
Head start closed tenpai is usually instant riichi. Please pin this down rst. Then, in what
kind of cases should we go dama (or break tenpai)?
When to go dama
Going riichi or dama will have no eect on nal placement For example in the following
kind of cases:
In all last, in the lead with a yaku-having tenpai (with yakuless tenpai, riichi is the correct
decision unless falling under one of the cases discussed later).
In all last, and even with riichi (tsumo or direct hit and ura 1), the nal placement would
not change (for example a pinfu dora 1 tenpai when behind a non-dealer by over 16000, but
being able to secure 2nd place with dama)
In the round before all last (South 3 in a hanchan), and winning with dama would give us
enough points that no one can overtake us in all last even with haneman tsumo.
Another player is close to busting out, and tsumo or direct hit on that player would let us
nish 1st.
1.2. HEAD START TENPAI JUDGMENT 45
Situations where the point standing inuences the riichi decision are mostly conned to South 3
onwards and an opponent being close to busting. (Although there are exceptions, the factors below
become more important.)
Dama is expensive enough, so that the point increase from riichi is inecient
Conrmed dama baiman and up
Conrmed dama haneman, except with a good wait in the early game
3 han 60+ fu hands (example: wertlllzzz777, riichi tsumo and dama
ron are both mangan)
Dama mangan
[long discussion of a simulation and Totsugeki Tōhoku’s book, with the main points being]
Good shape riichi wins about 50% of the time. Dama only increases this by about 5%, so
riichi is good.
With bad shape, go dama from the 12th turn onward.
However, if there is a possible improvement to the bad shape, going dama early is good.
With bad shape 5200 dama, riichi if there is no possible improvement outside of the late game.
Riichi good shape has a higher win rate than dama bad shape.
Additionally
Ryanmen dama mangan
Dama from the 13th turn (if about 1.5 players are attacking, riichi except just before a
draw)
Ryanmen dama 6400
Dama from the 10th turn
Bad shape dama mangan
If about 1.5 players are attacking, dama from the 13th turn
If 1 player, mostly dama
Bad shape dama 5200
If about 1.5 players are attacking, dama from the 14th turn
If 1 player, dama from the 8~9th turn
Bad shape dama 6400
If about 1.5 players are attacking, dama from the 11th turn
If 1 player, always dama (However, bad shape 6400 is often chiitoitsu dora dora or a
san’ankou with improvement to suuankou so dama is already quite probable.)
46 CHAPTER 1. TILE EFFICIENCY
Win rate maximizing damaten
There are some situations where it’s good to dama even medium-scoring hands (good shape 4 han
30 fu and up, bad shape 3 han 40 fu and up) outside of the late game.
Situations where winning is much more important than the added points from riichi
from a point standing perspective
Essentially, this refers to having a decent lead in South. (In East, you usually still want to push
for more points even when in the lead).
Example: South 1 or 2, 1st place and ahead by 12000 points, tenpai for dama mangan
with good shape Getting a dama ron here will create a 20000 point lead, which is safe even
against baiman tsumo or haneman tsumo when dealer. Direct hit on 2nd place creates an even
bigger lead.
Example: South round, 4th place, 1st place has an overwhelming lead, and dama
mangan ron would get us 2nd place
Situations where the win rate dierence between riichi and dama is extremely large
Example: Chiitoitsu dora tanki on a terminal or honor A dicult to use dora will ow
out easily. On the other hand, a middle tile dora will not come out easily, so with a middle dora
tanki riichi is relatively eective. Chiitoi dora dora with a non-dora honor wait is similarly also a
good situation to riichi.
When it’s clear that our target tile is unneeded by at least two other players Concretely,
players that have already cut it, are going for a single suit hand in a dierent color, are going for
kokushi or chanta-type when the target is a middle tile etc.
When our own discard pile is especially easy to read, and it’s clear that our target tile
is unneeded by at least one other player
Defensive damaten
This is the case where we don’t riichi to avoid losing points.
When we’re rst to tenpai, cases like this are quite rare, but they do exist. We will examine a
few situations where we might be prone to hesitate.
All last, 1st place, yakuless tenpai
Unless there are plenty of opportunities to create yaku (including calls that lower value), riichi.
Exception From the mid game on, when we only need to avoid the dealer and have enough of a
lead (at least 4100) or in the endgame when a draw seems likely.
1.2. HEAD START TENPAI JUDGMENT 47
All last, when riichi would lower our rank
Here too, if we’re rst to tenpai, the general rule is head start riichi. However, if any of the other
two opponents are already tenpai, it’s better to dama.
Furiten
For win rate, furiten ryanmen riichi bad shape riichi < furiten sanmenchan riichi < ryanmen
riichi. (Furiten ryanmen has a slightly lower win rate than bad shape.) However, furiten ryanmen
riichi is always menzen tsumo, so it’s worth more points. Therefore, we should riichi with furiten
ryanmen about as often as with a bad shape. On the other hand, furiten bad shape is extremely
bad.
With an open hand, furiten ryanmen < bad shape. This is because it’s harder to pressure oppo-
nents into folding. If everyone goes betaori, then the disadvantage of furiten essentially disappears.
Therefore, with an open hand, we should take a bad shape that avoids furiten.
Extremely bad wait (less than 2 tiles and not an honor wait)
The so-called ultra bad shape. When calling riichi on the 10th turn, this shape has a 14% win rate
and a 19% deal-in rate, so we should dama everything other than yakuless dora 3. However, on the
6th turn, deal-in rate is high, but win rate is around 30%, so riichi even with 5200 is good.
Example tuaassddvbnm.. dora 4
If y has already been cut twice, it’s not only ri but also etuo. that improve the
wait. When the original hand is bad, the quality and quantity of possible improvements increases.
Accordingly, with an extremely bad shape tenpai from the mid game on, stay dama and try to
improve the shape and riichi, or aim for formal tenpai if the shape stays bad.
Bad shape non-dealer riichi only, in the mid-late game
If we’re dealer and can’t improve the wait easily, we want to riichi and attempt to renchan (a
renchan is worth about 650 points on average).
In the mid-late game, riichi only as non-dealer is sketchy. The expected value is close to zero,
so the riichi decision will depend on the situation. We should especially avoid riichi when leading
in South, when someone has made a threatening call and appears close to tenpai, or when there
are less than 3 draws left.
Wait improvement judgment
Trying to improve the wait (“hand change”) when already in tenpai means we have to delay riichi,
and is basically a loss. It’s better to aim for improvement before tenpai, because there are usually
more ways to improve. Waiting for improvement while in tenpai is only worth it when there are
many tiles that will improve the hand. The following is based partially on simulations by Totsugeki
Tōhoku, which however do not account for the fact that having the initiative over opponents is an
advantage, so the limits have been made stricter.
48 CHAPTER 1. TILE EFFICIENCY
Requirements for hand change
Early game (4th turn): 6 types to double value, 9 types to improve the shape. (assuming 4
tiles per type, so 2 types of 2 tiles each count as 1 type)
Mid game (7th turn): Respectively 7 types and 11 types.
Mid game (10th turn): Respectively 9 types and 11 types.
Late game (13th turn): Don’t bother. At this stage, it is often better to dama or fold when
the hand is very bad.
These counts include the winning tile.
14
However, it’s often easier to hand change if we break
tenpai.
There are often situations where a tile will multiply value by 3 or 4. However, with hand change
quantity > quality.
So let’s look at some examples where we would still want to wait for a hand change.
Hand change patterns
A Double serial shape Each serial shape (errt or erty) creates 4 possibilities for
good shape, so 8 in total.
Example rtyuosdfgxxnm,dora 4 cut o
The point increase is very large, so we hand change even in the mid game. If the nm, was
m,., we only gain pinfu instead of pinfu tanyao, so we riichi in the mid game. If the nm,
was ..., we riichi even in the early game.
B Serial shape + oating tile which is dora or gives yaku
Example qwedghjkzz/m,. dora 4 cut d
Example qweasdgghjkcc3dora 4 cut 3and dama to make
sanshoku with c or ittsuu.
C Tanki shape Complex waits and tanki waits are the easiest to hand change. If we have a good
tanki, we can riichi.
Example With chiitoi, hand change to an honor, walled o tile, dora, dicult to use tile etc.
Example wrfffhjkzxcvbndora 4 cut w
14
TN: Dama tsumo into furiten riichi is sometimes playable, for example with doraless qwertys
dxcvnnfcutting qfor mangan or haneman. At least that’s what I think he’s referring to. See zeRo’s
book for a discussion of this play (“absolute pinfu damaten”).
1.2. HEAD START TENPAI JUDGMENT 49
D Callable shape Being able to call eectively increases the amount of available hand changes.
Especially common is changing a cheap call into a single suit hand.
Example tyuiooasq
q
q
5
55dora 4 drop as
E Few types change, but the point dierence is striking These don’t t into the framework
described above, but are still notable.
Example qqqwwwtuiooohj drop hj
Example qweaasdjklcb.. cut b
Example qqqssdffllccc3 cut 3 and dama.
With sddff or sdfff, riichi.
Exceptional hand change waits
Usually, we want to either riichi immediately, or break tenpai to maximize the probability of a hand
change as a general rule. Outside of late game hands with bad shape and many changes (tanki
etc.) where a draw is likely, or expensive hands (over 5200) with a yaku that have a hand change
to better shape, there are some situations that don’t fall under this.
Cheap hands with yaku, going dama versus breaking tenpai
Example East 1, East seat, 7th turn ertyifgghcvbngdora i
cut cand dama
Cutting i and breaking tenpai gives the most hand changes, but because i is dora, dama
tenpai with c gives change on yio (for sanshoku) and a win on u, which is better than the
hand change on zxcvbm on cutting i. The advantage of being able to win on u for
3900 or 2000 all is bigger than hand change in souzu. If i wasn’t dora, cutting it for hand change
would be good.
Example West seat, 5th turn qweerpyggcvbnndora e
cut yand dama
Cut n gives hand change on qwrtuxvbm, cut y on r (with tanyao) and
dfghxvbnm. We can’t ron, but the mangan tsumo on gn shifts our preference
to the latter.
When the hand changes in iishanten and tenpai are comparable and the loss from not being
able to win is big, it’s often better to take dama tenpai.
50 CHAPTER 1. TILE EFFICIENCY
When to break tenpai even though dama has many changes
Example qweerttyudfcvbdora b cut e
The provisional tanki shape (cutting d or f) has the most changes, but cutting e gives
ryanmen tenpai on qwrtuisg and can upgrade to tanyao and/or sanshoku. Cutting
q conrms tanyao, but loses the opportunity of drawing another q for takame sanshoku.
When two triple waits (here qru and wti) remain and there is an upgrade in score
(tanyao, sanshoku), breaking the tenpai excels over provisional tenpai.
Example erttyuuioasdm, cut m or ,
Cutting u only gives pinfu, so it’s not worth the loss in speed.
Example werrtydffgghvb cut v or b
Taking the tenpai is good, but if we really need mangan, we can cut r.
Wait choice
Which wait to take when in tenpai.
Of course with two equally wide waits, we take the more expensive one, and with two equally
expensive waits, the wider one. With two equivalent waits, we take the one that’s easier to win.
From erpty, we take the wtwait over the eywait as it’s closer to the outside. Between
kanchan and shanpon, we take shanpon. (If the shanpon has one tile less but includes a terminal or
honor, it’s still preferable. If it’s two tiles less, take kanchan unless the shanpon is on a live honor.
However, the read of the table is arguably more important.)
So we’ll consider the situations where one wait is expensive and narrow and the other is cheap
and wide.
With riichi
Point values are for ron with no ippatsu or ura.
Good shape 1300 > bad shape 2600. This is often with a ety where e is dora or a
ddfggh shape. The tile next to the dora and the iipeikou shape tend to be harder
to win on.
Good shape 2000 < bad shape 5200. But from qwertyuo cut o for the triple
wait.
Good shape 2600 > bad shape 5200. Similar to the rst one, but between ryanmen riichi dora
and shanpon riichi dora 2 or 3, choose the latter.
Good shape 2600 < bad shape 8000.
1.2. HEAD START TENPAI JUDGMENT 51
Good shape 3900 > bad shape 8000. The gain from ippatsu and ura is maximal at this score.
But from qwerptyuo, cut t for a suji trap.
With calls
Good shape 1000 > bad shape 2000. Neither has a big enough inuence on placement (it’s
an “interrupting hand”). This is not the same as pinfu only riichi (also 1000 versus 2000),
since pinfu riichi with ippatsu, ura and/or tsumo is worth about 3500 on average, while the
win rate reduction is less than half.
Good shape 2000 > bad shape 3900.
Good shape 2000 < bad shape 5200.
Good shape 2600 < bad shape 5200.
Good shape 3900 > bad shape 5200.
Good shape 3900 < bad shape 8000. This gets close in the mid-late game. Also, between
ryanmen yakuhai aka dora and yakuhai aka dora tanki, the former is better because dora is
dicult to ron.
Good shape 5200 > bad shape 8000.
Good shape 8000 > bad shape 12000.
With all of the above, if the bad shape is a wait on the dora, the good shape is better.
This can get even more complicated when taking into account takame-yasume situations and
the possibility of going dama.
Takame-yasume
The basic rule is: without any dora, take the takame-yasume. As the number of dora increases, the
preference goes to win rate and conrmed yaku.
Example East round, East seat: weeasdfghcvb11
With 0 to 1 dora, shanpon riichi. With 2 dora and up, ryanmen riichi. (If eis dora, shanpon
riichi.)
Example werasdffghjkmm
With 0 dora, cut f and riichi. With 2 dora, cut a and riichi. With 1 dora, it’s close,
depending on how likely l appears to come.
Example weeaaadfgxxxmm
With 0 dora, it’s sketchy. If the shanpon would be on an honor or we really needed points,
shanpon riichi. Otherwise ryanmen riichi. With 1 dora and up, always ryanmen riichi.
52 CHAPTER 1. TILE EFFICIENCY
Same number of tiles, score versus win rate
Example werfghnnm,,.55, with 5 cut once
Take the shanpon riichi, even though it’s slightly cheaper.
Example wweeaaffhzzbb3dora h, 3 is a guest wind
Dora tanki riichi
With b/, 3 tanki riichi
With 3 dora, dora tanki riichi and dora tanki dama are both good
With b/ and 3 dora, dora tanki dama is quite good
Example wweeaaff;zzbb3
g tanki riichi
With any other dora, 3 tanki riichi. (However if the wait is cut twice, riichi on the other
one. Don’t hell wait.)
15
Case where the wait with less tiles left has a higher win rate
Example qqqrtyudfgjkl3
In the very early game (around the 3rd turn) when opponents are not yet done discarding
lone honors, 3 tanki riichi. Otherwise nobetan riichi.
Yasume-takame good shape versus expensive bad shape
Outside of all last where we need a big hand for placement, riichi with the good shape. Good
shape riichi > bad shape dama.
Some exceptions:
Example weasdjklzzzxc
When q is dora, riichi makes it very hard to come out.
Example qweadfjklzzzxcdora a
Cut f and dama (with a not dora, f riichi is good).
Example weeaaasss..555dora 5
Cut w and dama (without dora, riichi).
15
TN: Heresy. Believe in the ow!
1.3. CALLING EFFICIENCY 53
1.3 Calling eciency
Calling tile logic
So far we’ve discussed closed hands that aim for riichi. We’ll now take a look at hands where we
have called or have the option to call.
Going for closed tenpai every time is a simple kind of mahjong, but it won’t bring home the
bacon. Even with a perfect iishanten like fgxxnnm, it’ll take between 6 and 7 rounds on
average to reach tenpai. Getting a closed tenpai means we got lucky.
That’s why calling eectively is extremely important. Since we’ll need at least 1 han from yaku
to be able to win, we’ll discuss tile eciency that takes yaku into account.
Each call we make can help the shanten advance by 1. Since advancing the shanten is harder
when closer to tenpai, it will often be most eective to call when close to tenpai.
That’s why, with an early game hand that’s far from tenpai, we will more often try to plant
the seeds of a yaku instead of focusing only on tile acceptance. Yaku building is not just
a skill to create big scoring hands. Rather, it’s also eective to bypass the 1 han limit and
increase the win rate.
Now, what are the concrete ways in which tile eciency changes when considering calling?
The value of isolated yakuhai increases
Usually better than a terminal that can’t connect to yaku or dora, but when winning closed looks
tough and we have several single yakuhai, there are cases to prefer them over bad shape joints or
oating middle tiles.
Example qwyysfllccbm56 cut q, going for yakuhai, open
tanyao or rarely chiitoi.
To the extent that we want to keep these single yakuhai and stack them, it’s standard to
open the hand for yakuhai pon. Conrming a yaku is just as good as advancing a weak
spot. From an eciency standpoint, it only makes sense to ignore a possible yakuhai pon when a
fast and expensive closed hand is in sight.
The preference for paired joints increases
Since we can call both pon and chii.
Example wwwyuidfkkccbm cut m
Also, in callable hands, a bad shape joint is preferable to a oating tile since it can be chii’d.
In callable hands, we’ll often want to x a bad shape complex joint that gives yaku and reinforce
elsewhere. In a closed hand, xing a bad shape joint is rare.
Example rrtaasfghklm,, cut a
With too much joints, dropping the weakest one and reinforcing the remaining ones is common.
However, there are also cases where we can keep a tile that creates yaku. When going for a single
suit hand, we’ll often drop a joint (rarely, an entire group) of a dierent suit and hold on to several
oating tiles.
54 CHAPTER 1. TILE EFFICIENCY
There are many people who hesitate to call when far from tenpai, but it’s exactly because
the hand is far from tenpai that we must try to call. Cases where we’ll call and then decide
to fold will not be uncommon. If we get into a situation where we can’t win no matter what, it’s not
too late to defend, but there are many point losses that can be avoided with a quick win. Attack
is the best defense.
Calling judgment
With calling, as with any skill in life (?), there are three main skills to know:
1. When to call
2. How to make easy to call shapes
3. How to make yaku for calling to work
When to call
Much can be said about deciding whether to call or not, but the fundamentals are speed and
value. We always have to think of the dierence between the shape after we would call or not
call. We can’t compare a 1000 point bad shape open hand to a riichi pinfu tanyao we couldn’t
possibly have gotten with the hand. If the closed hand would be fast enough and expensive, we can
ignore the calling opportunity, but if it would be slow and not that much more expensive, we’ll call
aggressively.
Example eriisdfhjjnm,dora 3 chii or pon into tenpai from
the 8th turn on. Yep, even with this delicious mentanpin dora 0. If an opponent looks like he’s
already tenpai or we’re the dealer, it’s good to call even earlier.
With a 1- or 2-shanten hand with a bad shape and a conrmed yaku, we’ll want to call even
more. Yakuhai are usually already 1 call down, so same story.
As a general rule, once we’ve called, it’s no problem to advance the hand with more
calls. It makes the hand faster while not making it cheaper.
Example dfghjxv..4
5
55 chii sgk into tenpai
However, calling decreases the number of available tiles, and when we don’t have sucient shape,
it weakens the rest of the hand, making it harder to reach tenpai and easier to end up with a bad
shape. It also becomes harder to integrate yaku and dora. Thanks to these factors, there will be
some exceptional situations where we’ll refuse to call even with an open hand. To say it in other
words, calling further is no problem if we can already concretely envision the 4 groups and the pair.
What about calls where the yaku isn’t conrmed, or leaves the possibility of kata-agari (when
only part of the wait has yaku, a.k.a. atozuke)?
Indeed, just like it’s better to complete bad shapes rst and end up with ryanmen, it’s better
to conrm the yaku rst. But here also, we must compare the speed and value dierence between
calling and not calling. Thoughtlessly hating kata-agari is nonsense. With a hand that would
be too slow to nish closed, call from anywhere; with a dicult to nish hand call only
the weak spots, conrming yaku or eliminating a bad shape.
Example opening hand, qydgkzxx.5677dora t insta-call 7
1.3. CALLING EFFICIENCY 55
This is a pretty bad haipai, but if the 7 comes we’ll pon it and cut q. In the distant future,
once our isolated tiles form joints, we’ll be able to call them. If a f comes out after, we’ll ignore
it as the shape has no completed groups yet.
Example 4th turn, wuoghhzz/n577 dora q pon 7cut w
We have enough group candidates and pairs, but no group yet. Consequently, the loss in
eciency from calling shrinks. Furthermore, if we don’t call, the hand will likely become too slow.
7 is obvious, but we’d call anything else cutting w, not caring about the obvious atozuke.
Kuikae and kuinobashi
These plays
16
are commonly hated, but getting extra value or improving to a good shape in 1 turn
is great value. We should proactively use these techniques when calling.
Example Kuikae nashi rules, West seat, dora x
xccvbnm,3344
4
pon 3 and cut c
chii . and cut c
chii x and cut ,
chii / with cv and cut ,
chii n and cut c
Planning yaku for calls
Which is the best yaku for calling?
Getting to tenpai closed is possible at most once in every four hands. With most hands, closed is
too slow.
17
In practice, about half of all wins are open.
Since calling requires a yaku, we must try to somehow create one when a closed win seems
dicult to pull o. Now, what yaku should we prefer for calling with an average hand?
Diagram of open yaku preference
based on ease of making, score and ease of using dora
16
Kuikae refers to calling chii on ryanmen, then discarding a tile that would also have completed it, for example
/
cvcut x. It’s illegal in many common rulesets. Kuinobashi refers to any call that doesn’t advance shanten
but still increases score or improves the wait, especially a call while already in tenpai.
17
As the level of play increases, so does the average tenpai speed. In Houou South, the median speed for declaring
riichi is already on the 8th turn, and open hands are usually even faster! ざわ(Source: https://blog.kobalab.
net/entry/20180118/1516202840)
56 CHAPTER 1. TILE EFFICIENCY
Rank Yaku
A+ open tanyao, yakuhai
A honitsu (chinitsu)
B+ toitoi
B sanshoku doujun, ittsuu
B– chanta (junchan)
It’s okay to never win the other open yaku (doukou, honroutou, shousangen, etc.) in an entire
lifetime :^)
18
If a rare hand where they’re possible appears, we can consider going for them.
Even a low-ranked yaku is a priceless treasure if we can’t see a higher one. Although we
tend to keep chanta and friends at a respectful distance because they’re dicult to make and cheap
when open, we should go for them if we can’t see another yaku. To repeat: we can’t compare them
to a mentanpin that would be impossible anyway.
Prefer conrmed (easy to conrm) yaku
If it’s easy to conrm, it’s easy to make, simple as that. If we can avoid kata-agari, we should go
for it, unless there’s a dierence in score.
Example rpyyii;jv/mm77 cut 7
Example qqwryfhzxvnm,. cut h
Cutting w gives the two alternatives of sanshoku and ittsuu, but ittsuu is one tile closer and so
we should cut h according to the “mentor theory”.
19
Furthermore, if the pair of q was a middle
pair, we should go for the superior pairing of sanshoku and open tanyao and cut z.
Dora
Dora has the best cost-performance of any yaku, but doesn’t count for the 1 han limit. In other
words, once a yaku has been conrmed, there is nothing more powerful than dora. 1 han call
+ dora 3 for mangan is the win with the best cost-performance. With mangan in sight,
we should prioritize speed, but to create mangan and above, it’s no problem to make even quite
painful calls.
Example tyzxv/.. m,
.
5
55 dora . cut x ignoring
honitsu
Example qwerruo
/
cv5
5
5dora u pon rand dora tanki
How to make open yaku
We’ll explain the tricks to making each of them one by one.
18
maicry.png
19
It said メンター理論, I have no idea what this means but it sounds cool.
1.3. CALLING EFFICIENCY 57
Tanyao
The indispensable linchpin of calling. An ace that’s fast and can use aka dora easily. Always be
conscious of it.
Example yioofhhjccvbbm cut o
When there’s no special dierence in tile acceptance, aim for tanyao right away. It ts closely
with the principle of tile eciency that closer to the inside is better.
Because kuitan is an extremely convenient yaku (especially with many dora), making calls that
don’t advance the shanten but conrm tanyao are seen frequently. Let’s memorize the following
kind of play:
Example weerriihkbm,. dora h chii j or n, cut .
Yakuhai
1 han in just 3 tiles, an important yaku together with tanyao.
Keeping single yakuhai in a faraway closed hand is more eective when we have several. The
probability of stack one pair with 567 is bigger than completing a ryanmen (9 tiles versus
8). We can also combine them with other yakuhai, toitoi, honitsu, chanta etc. to increase both
value (especially from 3 to 4 han) and speed. Keeping these single yakuhai over bad shape joints
or oating middle tiles is done to increase our own chances of winning and our score to
the utmost, and not for choking opponents. There are many players who keep these while
narrowing their hand “for some reason”.
Single suit
An excellent yaku that’s comparatively easy to make and can count on a high score. If we have
gathered enough group candidates for the 4 groups, it’s ne to aim for it.
In a closed hand that looks slow and cheap and doesn’t have enough group candidates, we can
sometimes try to force a single suit. In this case, even the humble single guest wind can become
a group candidate. On the other hand, when a hand like riichi + α or yakuhai dora dora is in
sight, we do not approve of discarding tiles in the other suit left and right. Though this can be said
about any yaku, not making an obvious open hand because one is being choked out of useful tiles
is nonsense. No matter how much we get choked, open is still faster than closed. Rather,
we should think of it as slowing down the opponent’s hand. To insist: we can’t compare the open
honitsu to a closed chinitsu that only exists in our dreams.
Toitoi
We often have to choose whether to go for toitoi or chiitoi. In what kind of cases is each of them
good?
When to go toitoi
We have a closed set
With 4 pairs and 1 set, calling pon and going for toitoi is usually easier to win. Rather than
58 CHAPTER 1. TILE EFFICIENCY
chiitoi 1-shanten for 9 tiles, a callable 1-shanten for 6 tiles is often faster, even when the tiles
are hard to call.
We can add yakuhai or honitsu for more points
According to the mangan theory, we should go for toitoi even with no set. Toitoi also often
combines with yakuman :^)
Many easy to call pairs (honors, terminals)
Needing to win a hand in all last
Calls are great here :^)
We can go for yakuhai aka or tanyao aka as mainline and make toitoi if we get
lucky
When to go chiitoi
We don’t have a set
We have no other yaku Because we can increase the value of chiitoi with riichi.
We have an isolated dora
The pairs are hard to call
No problem with chiitoi :^)
We can also see a group hand
Sometimes happens when we have many iipeikou-type shapes.
We have a big lead
For defense.
Sanshoku, ittsuu and chanta
We can get these with luck, but we won’t specically aim for these closed unless we really need an
expensive hand. Their cost-performance is not that good, and chanta also prohibits aka dora.
However, in a hand that doesn’t have any other yaku and is full of bad shapes, these three
can be great for getting that 1 extra han. Strong players are uent in taking these hands to the
win. They don’t advance shapes like qwryio closed unreasonably. No way that completes
closed.
We’ll sometimes see hands where several of these yaku are possible at the same time (“balanced
scales”).
Example wasdfjkklzc67
From this bountiful hand we can see pinfu, yakuhai, sanshoku, single suit, ittsuu and chanta.
We can imagine many dierent alternatives as the hand advances.
Even without a conrmed yaku, if the hand is too slow closed, we should see the possibilities of
dierent yaku and try to win using calls liberally.
1.3. CALLING EFFICIENCY 59
Principles of calling
The majority of yaku should be called “whenever possible”
First of all, hands that are at least 5200 with calls, we usually call. With hands that score 3900
but are wide, it’s usually still good to call from anywhere unless it’s the early game and riichi is
realistic. Then what about cheap hands that have the potential to be fairly expensive closed?
Example weryuufgkkcvb dora 4 call anything from the mid
game on
Even though this perfect iishanten for 6 kinds, 20 tiles can be mangan closed and becomes 1000
open, it’s good to call from the 8th turn on. If an opponent looks close to tenpai, we can call
even earlier. (However, if it’s important to make a big hand to secure placement, there can be
rounds where we’ll ignore calling even late.) With a hand like this that we want to nish closed
if possible, the conclusion is nevertheless to call for tenpai from the mid game on. With hands
that are harder to complete closed (bad shape 1-shanten or 2-shanten), it’s usually best to call if
possible. However, that doesn’t mean we can just call anything. If we can’t see the possibility of a
yaku, there’s no choice but to advance closed.
Yaku aren’t just important for score, but also for speed
Since yaku enable us to call, they make the hand as a whole able to accept more tiles. With pon,
we can accept 4× as much tiles, and with chii, 2× as much. (In reality this will be less, because
opponents will often need the same useful tiles and will sometimes even choke us.) Since putting
priority on tile acceptance close to tenpai is the principle of tile eciency, we should try to create
opportunities for yaku in the early game, since the gain in eciency if they pay o is enormous,
especially in a hand that would otherwise be slow.
When deciding what yaku to go for and when to call, decide based on the current
hand, turn and point situation
Of course, winning with an expensive hand is ideal, and ittsuu and chanta are harder to make than
tanyao and yakuhai (and often cheaper when playing with aka). But in mahjong, we can’t always
go for the ideal hand, since 3 times out of 4 an opponent will have a better hand and we’ll have to
cope with a worse one. While chasing the weaker yaku for no reason is to be avoided, if we can’t
see another path to victory, we have to go for them. If the hand is winnable, we should win
it.
Example qeyisfjlzcm.33
With a hand like this, not going for chanta and thinking pinfu is easier to make is a mistake.
Rather, this hand has sucient joints and is hard to win outside of chanta (+ sanshoku if we get
lucky). Furthermore, not wanting to win a 1000 with 2 calls because we’re behind by some points
and persisting for riichi is not good. The probability of reaching closed tenpai fast enough with a
hand like this is extremely low. We should call any of wkx, with this hand immediately and
only keep it closed when behind in all last, or when we have a big lead and don’t care about getting
tsumo’d.
60 CHAPTER 1. TILE EFFICIENCY
There’s not really a need to think about our hand begin easy to read for opponents
Even with a hand like the above example, there’s not really a need to refrain from calling to not let
opponents know what yaku we’re aiming for. Once we conrm a yaku, it’s not really a problem to
get choked since we can call from anywhere. It only makes sense to refrain from calling when the
hand is close to riichi, and then being readable is a minor concern at best. Furthermore, calling
with a faraway hand can put opponents on guard, causing them to weaken their hands (blung).
It might sometimes make sense to not call to not expose an obvious yakuhai atozuke, since those
are very easy to choke, especially refusing a ryanmen chii, since those are the easiest to complete
closed. However, this case will often be connected to the hand being either very slow (don’t want
to call to weaken the shape too much) or very fast (want to riichi instead). It’s ne not to think
about opponents reading our calls.
Example qeuuosfg...77dora f chii won any turn
Avoiding kata-agari
Obviously, we should avoid it if comes at no cost in speed.
Example With open tanyao, cut w from wet.
Example rtyxcccvb77chii
j
hk cut b
Though we can switch to tanyao if we cut x and later draw n, we want the least amount
of yakuless waits possible.
However, just like with our hand being easy to read, it’s not necessary to consider this an
important factor when deciding to call or not. When we want to not call to avoid kata-agari, it’s
usually because we have insucient group candidates or because we don’t want to call from the
strongest joint rst.
It doesn’t matter that our calls give some opponents more draws
However, it also gives ourselves less draws. If we have the opportunity to call, but the tile is
marginal, and there are many other tiles we can use instead, it’s often better to decline and hope
to tsumo it.
Calling can only complete groups
Now, is it good to call anything with a slow hand that has a guaranteed yaku? It’s not necessarily
always the case. A call might advance the shanten without actually making the hand faster to
complete. We have discussed the 3 ways of advancing shanten earlier:
1. Making a joint from an isolated tile
2. Making a group from a joint
3. Making the head from an isolated tile
With a call, we can only do 2, but by narrowing the hand, we make 1 and 3 more dicult. The
principle of tile eciency is that tile acceptance close to tenpai is most important. With a hand
1.3. CALLING EFFICIENCY 61
that has diculty with 1 and 3, it becomes hard to get to tenpai early and we’ll often end up with
a bad shape. Furthermore, calling makes it harder to integrate extra yaku and dora.
However, in hands where the necessity of performing 1 and 3 is low (in a hand where tanki is
ne, or we can make a nobetan shape like qwer, putting 3 o is ne), in other words in hands
that have sucient group candidates, if we have conrmed yaku, it’s no problem to make one call
after the other. To put it in another way, hands with sucient group candidates can arrive at
tenpai through calls only, without the need to tsumo. Not calling with a hand like that is limited to
hands that are suciently fast and can make riichi (or semi-fast hands where we’ll ignore ryanmen
chii but call the bad shapes), or from the mid game on, hands that are too slow and would have a
low chance of reaching tenpai and calling would make it dicult to defend.
Even with insucient group candidates, it’s ne to call important joints that we would really
like to complete (like yakuhai pairs) and postpone 1 and 3 for later. (We call these kind of joints
weak spots.) Especially calls that conrm a yaku and allow us to call in the distant future are in
agreement with the principle of tile eciency. Even painful calls are ne if they allow us to conrm
a yaku and go for an uncertain but expensive slow hand, especially if the hand would be painful to
nish closed and we can still defend with an open hand.
Even with a riichiable hand, it’s often better to call to improve the shape
Since it’s good to call into tenpai from good shape iishanten with a conrmed yaku from the mid
game on, we’ll often play with an eye to keep the option to call. With a live pair of yakuhai, we’ll
try to play to leave a good shape once we call it, and going for a single suit hand, we’ll drop joints
of the other suits and keep single yakuhai.
Example uiosfhzzxcvb55 cut s
Seeing pon tenpai, ; or j tsumo. If 55 was aa, we’d cut z. With no ; left, cutting
h for a suji trap is good, preferring the fast tenpai over the upgrade with j.
Example ttuuiicvbnm,66 cut i
With y, becomes a ryanmen. If 66 was aa, cut a.
There are not many players who excel at calling and the construction of callable hands. (I don’t
consider myself one of them either.)
There are many dierent misguided ways of thinking about calling (however, there’s something
to each “misguided” way of thinking). There’s the yaku supremacists who only make yaku to create
big scoring hands and the menzen supremacists who detest ugly (yakuhai atozuke) calls. There’s
the defensive supremacists who are afraid of narrowing their hand too much with calling. There’s
the riichi supremacists who disdain yaku that are dicult to go for even in situations where going
closed is even more dicult. And there’s the nyaggers who’ll call anything... Indeed, learning the
skill of calling is dicult. But conversely, it’s also a realm where one can show one’s skill dierence
from other players.
62 CHAPTER 1. TILE EFFICIENCY
Dierences from closed tile logic
When calling (or considering it), the value of some joints and isolated tiles changes compared to
closed hands.
The value of pairs rises
Compared to joints that don’t contain pairs, because we can pon twice as much as we can chii.
Even in a 3-pair shape, we’ll often prefer keeping a pair. While compared to a bad shape joint, the
tile acceptance is balanced (2×4 versus 4×2), once we pon, the 2-pair shape that’s left is superior.
We also insure ourselves against shimocha or toimen discarding our bad shape wait. Of course, we
should still prefer a ryanmen over a pair, cutting u from weruuiaddcc
7
77.
Bad shape joints become better compared to oating middle tiles
Through the inuence of chii, the loss of 8 instead of 4 tiles of acceptance becomes bigger. Even in
a joint overrun where we’d normally prefer a oating tile, we should keep the extra joint.
The value of terminal and honor pairs increases
Because they’re easy to call. In a closed hand, we prefer middle pairs to create ryanmen, but in an
open hand, honors are the best. They’re also easy to fold with if necessary. But when comparing
a 2 to a 7, the ease of calling is similar, but the number of upgrades is double, so it’s common to
prefer the upgrades. Similarly, the easiest to call joints become preferable, but deciding which in
fact is is highly dependent on the discards (especially kamicha’s) so we should pay close attention
to them.
Joints that have a combo become even more valuable
In a closed hand, combos play a role, but usually don’t invert the basic ranking of joints and pairs.
But in an open hand, bad shape joints with multiple combos into ryanmen like sfhjk or
wrtyu become very strong. We should obviously call these to improve them into ryanmen.
This kind of call is called kuinobashi and is easy to overlook, so we want to pay attention to it.
Serial shapes become even more valuable
Chiiing any of etyi into rtyu or any of fgjk into ghhj (still, we’ll only
rarely call h with this shape) creates a ryanmen instantly and is pretty damn strong. While bad
shape joints also become stronger, this kind of shape is so good we should prefer it. Calling from
an insucient group candidate shape is often not very fast, but there’s a big dierence if shapes
like these exist.
1.4. YAKU COMPOSITION TECHNIQUES 63
Aryanmen and oating tiles seperated by 1 from a sequence (“ikken hiraki”) become
more valuable
But not by as much as the above. From eert, we can chii r for ryanmen, from dghj
we can chii f. We can in theory also call any of wety or gk, but the remaining joint
would be bad, and it’s often better to ignore this not very eective call as we can draw a better
tile, but if the turn is late and we want to rush tenpai, we can call. Because it has wider tile
acceptance and it’s easy to make pairs, the aryanmen is a bit better than the ikken hiraki. Their
overall precedence over other isolated tiles is not much higher than in closed hands since only the
chii into ryanmen is actually good.
In the next chapter, we’ll look into general techniques to make specic yaku and use dora,
centering on open hands but also considering closed hands for convenience.
1.4 Yaku composition techniques
Principles of yaku and dora
The most important things to remember about yaku and dora. In Japanese mahjong with riichi
and its copious amount of dora, making an expensive hand without any yaku is easy. Accordingly,
techniques pertaining to yaku are useful less frequently and have less of an impact on play than
those pertaining to basic hand eciency and dora usage. Therefore, when looking at the hand,
instead of rst thinking about what yaku to make, we should rst think about where to make
groups and whether going for riichi is realistic. (In Chinese mahjong, where riichi doesn’t exist but
a yaku is still mandatory to win, it makes sense to think about yaku rst.) That’s why in this
strategy guide, we rst discussed tile eciency focused on “where to make groups”.
If creating yaku or using dora is the most ecient move, we should play it
This really goes without saying. When comparing equally ecient (fast) alternatives, we should
always prefer the any that gives dora or yaku. The problem is when yaku and dora are not optimally
ecient, or when we have to compare them to each other. This chapter will center on such cases.
The value of dora and yaku changes depending on the existence of other dora and
yaku in the hand, and is therefore relative
In mahjong, each han up to mangan doubles the value of the hand, but any han above that are
inecient. Accordingly, when we have no other dora or yaku, we’ll consider them important, but
when the hand is already a conrmed mangan, the added value of extra dora or yaku is small.
(There will of course be cases where the point situation will make going for haneman and above
important, but in the majority of situations, going for the fastest possible mangan is good.)
Aim for easy to conrm yaku
If both are equally easy, aim for the most expensive one (not just han value, but stackability).
This the principle of comparing yaku. Unless the score gap is big, easy to conrm yaku are
preferable. This can also be said about comparing dora to yaku or yaku to speed. Chasing too
hard to get yaku is rare, and so is breaking down yaku that have already been created. With
64 CHAPTER 1. TILE EFFICIENCY
“conrmed”, for global yaku (tanyao, honitsu, toitoi) we mean that all the group candidates have
been gathered. For partial yaku (yakuhai, iipeikou, sanshoku), we usually won’t break them up if
the groups have completed (except in hands like qwasdghzxcmmm, calling riichi
when we draw q or w). Furthermore, hands where multiple mutually exclusive yaku are both
reachable (“balanced scales”, ryōtenbin) are often preferable, unless a wider or more expensive
shape exists.
Play to make dora and yaku easy to conrm
For example, when there are multiple ways to call a tile, we should expose the group that conrms
dora or yaku. From errty where e is dora, we should chii for
t
er to leave rty
which can slide to accept another dora. Same idea without dora ebut when chasing 345 sanshoku,
because there is a small chance we might draw y and prefer to cut e for defense. By exposing
the group which gives yaku, we make sure it won’t get destroyed.
Often, dora is more important than yaku
Because it’s easier to use. When deciding what yaku to aim for, the ease of using dora will often
be a deciding factor. But when we have no other yaku, yaku is more important than dora
because it allows us to call. In slow hands that are expensive even without using a particular
dora, it’s also better to go for a yaku that enables us to win.
When deciding whether to chase yaku, it’s not just important how close it is, but
how close another way of winning is
For example, since sanshoku requires 3 groups, in a hand with 2 groups already complete, we’ll
almost never go for it unless desperate for points. Conversely, when the hand is far from tenpai, it
makes sense to consider even far away yaku. Keeping isolated tiles that create value, and dropping
other joints when a tile sticks to them, all the time without decreasing shanten, is called watari-
uchi. In mahjong, since tenpai speed is the most important of all, the skill to chase yaku without
straining (slowing down) the hand is important.
On the other hand, in a situation with insucient group candidates, forcing a certain yaku by
dropping a joint (kime-uchi) is usually not done, even if the rest of the hand is strong. However, we’ll
see some exceptions to this rule when going for tanyao and honitsu, two yaku that are exceptionally
strong and allow us to call freely.
It’s most important to be good at making common yaku
This chapter will therefore focus heavily on the most common ones. For rare yaku, we can deduce
the kind of logical moves by analogy with more common yaku or by applying general rules.
Example In a far away hand, keep a in qqzza for sanshoku.
Example Pinfu iipeikou riichi > bad shape ryanpeikou
Example Ryanmen honitsu yakuhai 2 > tanki honitsu shousangen. Without honitsu,
we usually take shousangen.
1.4. YAKU COMPOSITION TECHNIQUES 65
Example With 2 kans down, we should make a 3rd one, but “going for” sankantsu is impossible.
Having discussed generally when to go for what kind of yaku, we’ll give a brief sketch of when
to go for each one in particular and the special moves for chasing them.
Tanyao
Extremely easy to make and callable without kuisagari, this yaku forms the foundation of mahjong
together with riichi.
Isolated tanyao tiles become more valuable
In a hand where tanyao is achievable, oating 2/8 >> single yakuhai. Even if tanyao isn’t
conrmed, if we have no other yaku, playing towards the center is standard.
23 and 78 ryanmen become much weaker (obvious)
If we can conrm tanyao, we usually should
Example weryudfgvvnn.. cut .
The exception is hands like weryudfgcbnn.. where to conrm tanyao we
have to sacrice a ryanmen riichi, similarly cutting t from wet even if the rest of the hand is
all tanyao.
Even if it lowers shanten, we can drop a penchan and keep a oating middle if it
conrms tanyao
Since we can call, it doesn’t just increase the score, but also makes the hand faster.
Example qwtuusssfhkvvb cut q
We can call without advancing shanten to conrm tanyao
Example weerr;jklccn, chii any of hm
Example qwertysfkkcn, chii any of ruand cut q
But with qwertyfgkknm4, we’ll prefer riichi pinfu, unless leading in all last
where score doesn’t matter.
Similarly, when score isn’t an issue, the following kind of big brain call is easy to overlook:
With the rest of the hand being zxcvgjj, cutting z after the chii:
errtty chii any of ru left with errt
rrttyu chii any of ey left with rtyu
wrrtty kanchan chii e left with rtty
66 CHAPTER 1. TILE EFFICIENCY
Pinfu
This is also the foundation of mahjong, but rarely something to aim for, more often just a bonus
for playing eciently.
Because pinfu means we have minimal fu, it’s not as good for scoring as the other 1 han yaku.
It’s good to not worry about losing pinfu with an otherwise good play. It’s common to prefer
another benet over pinfu.
Example qertyfgghjvv44 cut q
Temporarily sacrices pinfu, but the upgrades into good shape are more plentiful (honor tile
shanpon is also strong). If we draw the w, we cut 4 aiming for pinfu tanyao despite furiten.
However, with 5 han, fu no longer matters. It’s helpful to remember that pinfu tsumo + 4
han is one of the main lines to haneman.
Since a yakuhai pair invalidates pinfu, in hands where we have enough sequences and ryanmen
if we don’t have a head, guest winds become slightly better than yakuhai.
When pinfu is realistic, we’ll sometimes x a ryanmen pair into a ryanmen more often than
eciency alone would suggest. We’ll also prefer ryankan over penchan/kanchan pair.
Example wrtyyuasdllnnm cut n
Identical acceptance to cutting w, but the ryanmen kanchan (remember?) guarantees pinfu.
Example wryyisdfghzzm, cut y
Cutting w or i when the next group completes.
Example xccvbnmm,,ghll cut ,
This creates a double ryanmen kanchan waiting on any of zvn. (remember?)
Iipeikou
Like pinfu, iipeikou is another yaku that is rarely specically aimed for but comes naturally as a
reward for ecient play. The shapes that give rise to iipeikou like aryanmen and nakabukure are
naturally easy to extend and should be preferred over regular oating tiles.
Since iipeikou is a 1 han yaku only, when all other joints are ryanmen, we’ll drop a iipeikou-
giving bad shape joint rst. (As discussed earlier, good shape n han > bad shape n + 1 han.) Since
we already hold one tile of the wait, if another one gets discarded we end up with a painful ultra
bad shape. In this case, it’s often good to prefer a bad shape joint with 4 tiles left. (Again, a 2×
dierence in speed > 2× dierence in value.)
We can often aim for iipeikou with a “ying pairs” shape, creating two groups from it. This is
easy to overlook, so we should pay attention to it.
Example wertyuffggkkbm cut m
The tile acceptance is 2 tiles lower, but we cut m anyway (not b as drawing v is big here).
Making it easier to end up with ryanmen is an important factor too (pinfu, easier to win).
Example wertyussffhhxx cut x
1.4. YAKU COMPOSITION TECHNIQUES 67
Example qqeyyiidgxvm,. cut x
This is slightly inecient (3 pairs is bad) but leaves the tiles for iipeikou. If xv was cb
(inner kanchan), cutting y would be good (not i as we want to draw t for ryanmen).
wweeerrr weeerrrt
The two complex waits above also give iipeikou on w or t. This can be very easy to overlook.
Yakuhai pairs
Giving 1 han (or 2 han with double yakuhai, renfonpai) with just 3 tiles, yakuhai have an excellent
cost-performance value. This makes single yakuhai comparable to isolated number tiles, even though
they’re vastly harder to make a group with. There will even be hands where they are preferable to
joints. For this reason, the use of single yakuhai is extremely dicult and forms a major obstacle
to any systematization of tile eciency. We’d like to acknowledge that this section will therefore be
longer than those on other yaku and more theoretical. We’ll start with the more straightforward
discussion of paired yakuhai.
When to drop a yakuhai pair
Since we can call pon, a 2 pair shape of which one pair is yakuhai has an eective tile acceptance of
10 tiles (4×2 + 2). Though this will be slightly lower in practice as we’ll not always be able to call,
it’s still comparable to ryanmen. The honor shanpon when in tenpai also has a win rate rivaling
ryanmen. Therefore, it only makes sense to drop a yakuhai pair in the following kind of cases.
Conrmed pinfu iishanten But even here, if the advantage of keeping yakuhai is large, we
should keep it.
Example errtp;hjklzz77dora k cut z
A mangan even when called, and the shape after the call is very wide and guarantees a good
wait. When aiming for haneman and up, cut 7.
Example qqwweefgkkvb66dora 4 cut f
Preserves the option of going for chiitoi. The fg has a very slight overlap with kk, and
we can draw ; for chiitoi.
We can make tanyao without increasing shanten
We can cross into a superior yaku From honitsu into chinitsu etc.
Example xccvbnnm,,,.66dora . cut c
But with a hand like this which is already expensive enough, and the dierence is speed is large,
it’s better to take the straightforward win.
Conversely, there are also situations where dropping a ryanmen to keep a yakuhai pair is good.
68 CHAPTER 1. TILE EFFICIENCY
Example weyuifghxc5566dora 4 drop one of the ryanmen
Example qqerrtyb/jkl77dora q cut r
Taking tenpai even with w.
Should we 1-call yakuhai pon?
(By 1-call, we mean to open the hand and make the rst call of the hand.) Yes.
The exception is the following kind of cases:
We can expect a fast closed tenpai, for example an early game iishanten with 2×ryanmen
and a yakuhai pair, and calling would be cheap. We should especially not call if the closed
tenpai would be expensive.
Chiitoi iishanten (but if we can combine with another yaku for expensive toitoi, we can
call)
The hand is so fucked it’s better to go for kokushi musou
Not fucked enough to go kokushi, but the hand has no head, group or dora and
it’s already mid game, and we’re in the lead.
If the hand is very far away from tenpai, we should still 1-call in the early game. In the
future, once we tsumo some joints, the advantage of being able to call will be very big and have a
large impact on win rate. It’s not very important to think about defense in the early game. If the
tsumos are bad, we can start emphasizing defense from the mid game on.
Should we call for yakuhai atozuke?
When we have gathered enough group candidates
Example qeoonm,,77
j
ghdora 7 kamicha discarded w
If we chii it, our atozuke’s wait will become extremely obvious. Should we call? Our other
options to make a less obvious to read tenpai are w or 7 tsumo or 7 pon. 2 or 3 tile types is
not nearly enough to wait for a hand change, and we should always chii.
Example wwexxxmm55
s
dfdora 5 kamicha discarded q
Totsugeki Tōhoku wrote in his Scientic Mahjong
20
that we should chii, but should we?
We’ll apply the same theory as in the previous example. We get a less obvious shape with
qwrm5 tsumo, wm5 pon and r chii. (wm tsumo also open up sanankou, but this is
so rare of a benet it doesn’t really matter.) Depending on how we estimate the ease of calling
these, this is about 8 to 10 tile types, so we should chii from the mid game on.
Example oocv.66qq
q
l
l
ldora 6 kamicha discarded x
20
The famous and highly technical book which contributed signicantly to the popularization of digital mahjong.
It rst came out in 2004 and is now (2019) in its 22nd printing.
1.4. YAKU COMPOSITION TECHNIQUES 69
Adding to xb6 tsumo and 6 pon for a better wait, we have zm, tsumo for chanta,
cvtsumo for toitoi and the ultra spicy . tsumo for toitoi honroutou with a chance of sanshoku.
We should also ignore this chii in the early game and call from the mid game on, unless we really
want to score big. Furthermore, if o comes out, we should pon to assert dominance and cut v.
Because even in extreme cases like these, calling is good from the mid game on, it’s no problem
to call into yakuhai atozuke in cases where our yaku isn’t obvious to opponents even from a high
shanten. It’s really necessary to worry about getting choked.
Even when we could get choked, it’s more important to consider the turn and the
quantity and quality of improvements to the hand.
When we don’t have enough group candidates
We should obviously call the yakuhai, but calling the rest of the hand won’t always make it
faster. It’s good to only call weak spots that would otherwise be especially hard to complete, like
joints around the dora or with an overlap. Our judgment will often depend on the quality of the
entire hand and the turn.
Example 1st turn, qyasslcb,5677 dora t only call 7
Example 5th turn, wrybmsfhjkl77dora 4 only call 7or n
From the mid game on, call the rest too. (But g makes it harder to complete the head, so it’s
sketchy.)
It will also often depend on the discards and the opponents’ speed.
Another thing to pay attention to when calling for yakuhai atozuke is that the yakuhai can’t
become the head.
Example rrtvvbsdf77
m
n, cut t or b
Preserving the 2 head candidate shape. Pay attention to not cut r or v in this kind of
shape.
Single yakuhai
The value of single yakuhai
Usually, we think that 1 < single yakuhai < 2 < single renfonpai, but the inuence of the rest
of the hand is big. The value of single yakuhai increases when the hand is dicult to win (bigger
inuence on win rate) and when they lead to a strong hand (honitsu, toitoi). They also have the
advantage of often being safe when outpaced by opponents. Even with 1 tile discarded, we want to
keep them if a closed win looks dicult.
Example 1st turn, qwyiiddgjlxv56 dora t cut q
Even if we draw e quickly, the hand is still too slow and cheap, so we’ll try to go for yakuhai
or open tanyao.
70 CHAPTER 1. TILE EFFICIENCY
Example 1st turn, erassg;klvbn57 dora 4 cut 5 or 7
Even though the penchan shape is bad, this hand is already 2-shanten.
Example 1st turn, ertiiaskkl2257 dora 2 dicult
Already 2-shanten, but with many bad shapes and expensive even open. There’s also a possibility
of going manzu honitsu. Whether to drop as, cut an honor or cut kas a compromise is dicult.
Single yakuhai discard order
Because it’s good to deny an opponent the renfonpai (especially double East is scary), cut round
wind dragons seat wind. Though this is highly debatable, from guest winds it’s good to
cut shimocha toimen kamicha. We want to prevent shimocha calling chii on our discards,
while being able to chii from kamicha’s fast hand is an advantage. There’s also the advantage or
disadvantage of extra draws. But when there’s specic opponent we want to prevent from a quick
win, it’s best to cut his wind rst.
How to keep single yakuhai
Single yakuhai become better when we have several Because it’s easier to stack at least
one. In a slow hand with 3 dierent ones that has many bad shapes and no other yaku, we should
drop the weakest joint and keep the yakuhai.
Furthermore, when playing like this, oating middle tile > penchan. However, we’ll still
prefer a ryankan or inner kanchan over a single yakuhai, hoping to luck into drawing a sequence
rather than more yakuhai.
It’s often good to keep single yakuhai in faraway hands with too many joints
Single yakuhai become more valuable when we already have a yakuhai pair or set
Because it’s easier to go for honitsu and/or toitoi. We’ll discuss this in the respective section on
those yaku.
Sanshoku
Formerly known as the ower of the yaku, today we more often hear “don’t force sanshoku” and
“speed over sanshoku”. Both old style players who chase for it too much and players who overem-
phasize speed even when they should go for sanshoku abound. (The same can be said for many
other 2 han yaku.) We’ll try to explain using ideas from tile eciency when to see sanshoku and
when to disregard it.
If we can see sanshoku without a real loss, we should obviously see it. When comparing oating
tiles and joints of the same type, or when discarding e or y from erty, it’s important to
verify the possibility of sanshoku.
Example wrydfgcvvbn.. draw h cut d, draw s cut g
Example qwadhjkllzxcvb cut v
1.4. YAKU COMPOSITION TECHNIQUES 71
When comparing riichi pinfu and bad shape riichi sanshoku, the latter is preferable, especially
in a hand like the example where sanshoku is conrmed and pinfu isn’t. (We cut v over b to be
able to accept /.) The score is higher, and since we can chii (and we should on any turn unless
we need a big hand, since an iishanten with 2 bad shapes takes an average of 17 turns to tenpai),
the speed is comparable.
If qw were we, sanshoku is not conrmed but pinfu is, so dropping ad is good, going
for sanshoku only when needing a big hand and having no dora.
Example wertyasdfhllvn cut n
We can make conrmed 456 sanshoku, but the 3-sided wait and the amount of upgrades to
ryanmen make going for pinfu a bit better.
In general, bad shape joints that conrm a 2 han yaku are preferable to ryanmen, especially
when far from tenpai since they enable calling.
Example wryuiohhklvb,. cut w
Similarly, isolated tiles that can create sanshoku also become stronger.
Example qwetyuasggzm56 cut 5 or 6
Since making sanshoku requires 3 groups, when we have 2 strong group candidates outside of
the possible sanshoku, we disregard the possibility of sanshoku from isolated tiles. (The same idea
holds for ittsuu.)
Example qqetttyuhcvbnm cut h
The cvand qqettshapes are too strong to justify keeping hfor uncertain sanshoku.
While this example doesn’t amount to it, returning shanten to chase sanshoku is almost never done.
However, with too much joints, the loss from keeping an isolated tile for sanshoku while dropping
the weakest joint is small, even when being able to call.
Example wwrtuuioghbm22 cut 2
Taking a shape that doesn’t conrm sanshoku but leaves two alternatives is also often good.
Example ertyffglllvb,, cut f
This move foresees both 345 and 456, and is preferable to keeping the vertical acceptance for
riichi only. If l were dora, the added score from sanshoku becomes weak and it’s better to cut e
and maximize speed.
Example wertyuughhvvbn cut v
While cutting h enables both 456 and 567, the dierence in tile acceptance is very large and
so this move isn’t recommended. Cutting v for a very wide shape and a shot at 456 is better.
When considering WWYD problems about sanshoku, the following criteria will usually lead to
the correct answer:
Ease of conrming. In general, a sanshoku from an isolated tile is hard to conrm, while
sanshoku from a bad shape joint is easier, but people often seem to prefer the former.
72 CHAPTER 1. TILE EFFICIENCY
When hard to conrm, go for sanshoku when the loss in tile acceptance is small. When
close to tenpai, this loss becomes relatively bigger and sanshoku more dicult to make, while
far away from tenpai the advantage of making sanshoku is big. Old style yaku supremacists
tend to neglect the former, riichi supremacists the latter.
In fast hands where the benet of being able to call is small, go for sanshoku when the
marginal value of 2 han is large. With a conrmed mangan, sanshoku usually doesn’t
matter, but with no other yaku or dora, it’s very big. Here too, yaku supremacists tend to
neglect the former and riichi supremacists the latter.
We’ll now consider a few example problems based on these ideas.
Example weertuijklbbm, with no dora cut e, else i
Sanshoku is not conrmed (requires double takame), but the dierence in tile acceptance is only
4 tiles.
Example pydffhjzzzxcnm cut hj
Sanshoku is not conrmed at all (requires triple takame), so we cut the weakest joint since we
have too much of them.
Example errtyuigghjnmm cut n
Requires both of ,k for sanshoku, and the shape on cutting n is much wider.
Example tyyyuid;hjjknm cut i
While we can cut d and go for both 567 and 678, losing out on mangan tenpai with f is
painful. Cutting i for the easier to conrm 567 with b is better.
Example wrryuiojzzcbm, cut w
At this stage, cutting j which gives 678 or 789 is a no-go. The w move which preserves
2-shanten and a strong 2 pair shape is good.
Example tuiissdfgjccbm cut t
This hand is far from tenpai, but since we’ll commonly go for open tanyao making 567 closed
will be rare. Unless we really need an expensive hand, cut t.
Ittsuu
The theory of ittsuu is similar to that of sanshoku. When 2 good group candidates outside of
ittsuu have been gathered, we ignore it, but we prefer bad shape joints that guarantee ittsuu over
ryanmen.
Example qwrtyiollvbbnm cut vb
Example qwtyuiollvbbnm cut qw
1.4. YAKU COMPOSITION TECHNIQUES 73
Similarly, an isolated tile that can create ittsuu is stronger. The q in qrtyio is
obvious, but even the a in the uncertain afgkl shape is easy to overlook.
Example qwryuiofgcbm,, cut q
In this example, ittsuu is conrmed, but cutting qo for (open) tanyao is more eective. Same
as with sanshoku, it’s often better to not chase it too much when tanyao is available.
While sanshoku and ittsuu are mutually exclusive, there will be some shapes where both are
achievable depending on draws.
Example qwetuiodzxcvmm cut v
Example ertyiidxcvbnm, cut d
The above example has a big dierence in tile acceptance, so it’s better to go for ittsuu or
tanyao.
When we have to pick between sanshoku and ittsuu, we’ll think about the following criteria. In
general, it’s better to pick the more exible sanshoku which can stack with tanyao.
Ease of conrming
Strength of acceptance
Score depending on other yaku or dora
We’ll examine some example problems of this type now.
Example East round, North seat, 7th turn, dora ,
eeuisdghjklm,. cut gfor sanshoku
This is an iishanten with conrmed pinfu. Sanshoku and ittsuu both give the same score, so we
only need to nd out which one’s easier to make.
To make ittsuu, we need to drop uiand draw both a and fin either order. While drawing
f rst gives a 3-sided wait, we still only get ittsuu on a.
On the other hand, dropping gh for sanshoku only requires drawing o. If we draw it rst,
we can enter tenpai with conrmed sanshoku. Since sanshoku is easier to conrm, we should go for
it over ittsuu.
When going for sanshoku, we could also drop sdinstead of gh. However, the af wait is
usually easier to win. Also, cutting gand drawing n later allows us to shift over to 678 sanshoku,
which can stack with tanyao.
Example East round, West seat, 8th turn, dora o
weasdfgklzxcmm cut kl for sanshoku
Here, making sanshoku and ittsuu is about equally dicult, but going for sanshoku guarantees
pinfu.
74 CHAPTER 1. TILE EFFICIENCY
Example East round, West seat, 8th turn, dora d
weasdfghjlxcmm cut l for sanshoku
At rst sight, ittsuu is conrmed and sanshoku looks dicult to make. But even here, going for
the more exible sanshoku shape is better.
When going for ittsuu, we need to drop either of the ryanmen. If we draw k rst, we get pinfu
ittsuu, but if we draw the ryanmen rst, we get ittsuu with a bad wait.
On the other hand, when we cut l, no matter which of qrzv we draw, we can make
pinfu takame sanshoku, since we can slide in pinzu to make either 123 or 234. Furthemore, with
both r and v we get tanyao.
Toitoi
We usually start calling for toitoi when we have 5 sets or pairs. (Obviously, with 6 pairs we should
take chiitoi tenpai.) With no other yaku, calling for toitoi from 4 blocks or less is painful, but if we
can combine with another yaku like yakuhai, tanyao or honitsu, this is no longer the case.
21
Toitoi or chiitoi?
When to go toitoi
We have a closed set
With 4 pairs and 1 set, calling pon and going for toitoi is usually easier to win. Rather than
chiitoi 1-shanten for 9 tiles, a callable 1-shanten for 6 tiles is often faster, even when the tiles
are hard to call.
We can add yakuhai or honitsu for more points
Especially when we can still make a decent open hand even without toitoi. We can also hold
one extra tile in a non-toitoi hand and transition to it when we draw a pair.
Many easy to call pairs (honors, terminals) Even better when we can call a middle tile
to start.
Needing to win a hand in all last
Calls are great here.
We can go for yakuhai aka or tanyao aka as mainline and make toitoi if we get
lucky
Suuankou iishanten In general, we should call into mangan tsumo tenpai immediately from
this shape and only force suuankou if behind by a lot.
21
In modern meta, it’s common to force toitoi from 4 pairs 0 sets if it’s still the early game, there’s at least one
other yaku, and most of the pairs are easy to call. (look up トイトイダッシュ for examples and more strategy)
1.4. YAKU COMPOSITION TECHNIQUES 75
When to go chiitoi
We have a pair that has been cut twice and can no longer become a set
In this case, we’ll often break a set and force chiitoi.
We don’t have a set
We have no other yaku Because we can increase the value of chiitoi with riichi.
We have an isolated dora
The pairs are hard to call
We can also see a group hand with iipeikou
We want to play defensively
When in the lead, or there is an especially dangerous tile (daisangen threats etc.)
2 sets, 4 pairs Breaking a set creates an extremely wide iishanten that guarantees chiitoi
tenpai on almost any possible draw. But if circumstances for toitoi are good (yakuhai pair,
early turn), we can attempt toitoi.
Example problems
Example yyiiassdzznnm,dora n cut ,
Whether to cut any of adm, for chiitoi or s for toitoi.
With chiitoi, the hand accepts 9 tiles for 6400 dama. With s, the hand accepts 6 tiles (yiz)
for 2600 riichi and 4 tiles (u) for 5200 riichi.
While cutting s allows an upgrade to ryanmen with any of tbnm, including p/, it’s
still not as good as chiitoi. Also, dropping the dora onto the table constitutes a risk. We should
cut the least likely of adm, to be left in the wall, but in the absence of information, cutting
, allows us to cope with drawing /n.
Example yyuughkkbnnm,,dora , cut y
This problem isn’t easy. In practice, the two alternatives are y and g.
Cutting y emphasizes win rate. Calling for 3900 is the mainline, but adding aka, sanshoku or
dora pon makes it easy to reach mangan. Going for 567 sanshoku closed is unexpectedly problematic
as it requires letting go of a dora, so we should call any of pk/m, from the early game.
Cutting g preserves chiitoi iishanten with an outlook for a monster hand up to ryanpeikou.
While either is a correct answer, we recommend y. The main advantage of g is preserving
chiitoi, but the wait becomes bad, and calling a lucky dora or aka makes the yyuu shape
heavy. We think a 3900 minimum with good shape is the main idea.
76 CHAPTER 1. TILE EFFICIENCY
Example eeruuiiodf,,77dora 4 cut df
Cutting , is fastest, aiming for 7 pon into perfect iishanten. This kind of fast move that
ignores chiitoi is good when leading in all last. But it’s very cheap. Cutting 7 is the choice of the
menzen riichi faction, but it’s quite slow and not much more expensive, so it’s a bit lacking.
Dropping df is a move that aims for maximum upgrades into an expensive chiitoi or toitoi
hand. After 7 pon, it’s faster than cutting , and allows for a natural climb into toitoi.
While r preserves the chiitoi iishanten, forcing the df shape is a bit awkward, and breaking
up the er ryanmen makes the iishanten worse, making this the least skillful move.
Especially when playing without aka, ignoring toitoi/chiitoi with yakuhai and no dora makes
the hand very cheap. Dropping a ryanmen to preserve these yaku is an indispensable strategy in
aka nashi rules. In aka ari, toitoi and chiitoi become weaker because they have trouble using aka,
but even there df is the best move.
Example eeeiiaagg,4566dora 4 cut ,
With 1 set and 4 pairs, whether to keep the set or widen the chiitoi acceptance depends on the
hand. Keep the set when
1. there is a yakuhai pair or tanyao
2. there are no dead pairs
3. the pairs are easy to call (honors and terminals)
and force chiitoi when
1. there’s a oating dora (especially an honor dora)
2. toitoi would be 2600
3. there are many middle pairs
is the general theory.
In this dicult problem, whether to go for chiitoi or toitoi depends on personal preference, but
having polled some strong players, cutting , and calling from anywhere seems to be popular.
While the oating dora is cause for concern, the chiitoi acceptance is only 3 tiles lower, and toitoi
hatsu is often easier to win than chiitoi dora tanki. But since toitoi has trouble defending, if
defensive power is important, it makes sense to cut e. Toitoi is more proper to attack, as is chiitoi
to defend.
Example eeeiiaagg,,,66dora 4
This is either a very wide iishanten for chiitoi, or an iishanten for toitoi up to suuankou.
Here too, toitoi is preferable. While chiitoi gets to tenpai faster, it’s not that easy to draw a
good tile to wait on. It’s better to pon into tenpai quickly.
1.4. YAKU COMPOSITION TECHNIQUES 77
The problem is whether to ignore pon and aim for suuankou. In online mahjong without special
prizes for yakuman, it’s recommended to pon from the 6th turn on. Suuankou is the easiest yakuman
to make, but drawing one of the 6 needed tiles and then tsumoing on of the remaining 4 before
it comes out from an opponent is dicult, even more after skipping a possible pon. Since we can
tsumo sanankou after calling, we think it’s good to call here.
Chiitoitsu
For deciding between toitoi and chiitoit, see the previous subsection. This subsection will focus on
deciding between chiitoi and a sequence hand.
Chiitoi or sequences?
When far from tenpai, not deciding for either and preserving both possibilities is usually good.
However, there are some exceptional cases where committing towards one shape is better. This
is typically in hands where one of the two is dicult to achieve and can be safely ignored without
a major loss, while the committing move signicantly improves the win rate of the more realistic
alternative.
Example qqrdgjjzzcbb,. cut ,.
This hand is already 2-shanten for chiitoi, while making a sequence hand is very slow. Breaking
up ,. for chiitoi preserves a small chance of making 345 sanshoku.
In a hand like this with at least 4 pairs where the chiitoi shanten is lower than the group shanten,
and no possible draw can create a good group hand, committing to chiitoi is good, holding on to
isolated tiles that look easy to draw or easy to wait on. While committing moves that pointlessly
negate yaku just lower win rate, this kind of committing move improves speed close to tenpai and
is therefore in accordance with the principle of tile eciency. This isn’t just true for chiitoi, but
also for yaku like single suit or chanta, where breaking up a joint to keep a yaku-related oating
tile is often good.
However, if there are sucient joints for a group hand and we have a yaku that enables calling,
it’s often better to break up pairs and go for a normal hand. The loss from missing out on chiitoi
will be small since we’ll want to call in the majority of cases anyway.
When close to tenpai
The basic idea is to commit to groups when the group shanten is lower, make a mixed shape when
the shanten is the same, and preserve chiitoi shanten while leaving the option for a group hand
when the chiitoi shanten is lower.
Example werrtuiiokkxvv cut i
Example wwtuuffggxcvvb cut t
While a group hand with tanyao is very realistic, breaking up the y to preserve chiitoi is
actually faster. If tuu were yuu, lowering shanten and cutting f to commit to pinfu
tanyao is good.
78 CHAPTER 1. TILE EFFICIENCY
Example eetjkllzxxbbm. cut z
The group shape is not strong enough to commit to it, so we preserve chiitoi 2-shanten.
Example pyysdffhkxxvbb cut y
With tanyao, ending up with chiitoi will be rare, and the kmove that preserves chiitoi weakens
the group shape by a lot. Fixing the aka ryanmen is better.
Example wwerrtffhhjjvb cut vb
Preserving chiitoi 1-shanten while envisioning up to ryanpeikou with gk.
Example wwerrtffhhjjv/ cut h
With the aka in souzu, breaking up the souzu would be painful. We cut hseeing 456 sanshoku.
Example wwwerrffhhjjvb cut vb or j
Here dropping vb is also good, but if f or h is dora, aiming for open tanyao with j is
faster, creating a good shot at perfect iishanten with the next advance.
In the three examples above, we shouldn’t cut manzu as this would narrow the tile acceptance
towards a group hand too much.
Example wwrffgccvb1155dora r, East round cut c
Since we can and should call from anywhere, we can ignore chiitoi and cut c. If 1 were a
guest wind, we’d cut g preserving chiitoi. We’d still call 5, but the other calls would depend on
the circumstances.
Example errdfxxccvbbnn cut nearly and efrom the mid
game on
When preserving 1-shanten is important, cut e, but returning to 2-shanten with n creates a
better shape in the long term.
We should return a chiitoi 1-shanten into a group 2-shanten in the following cases:
The loss from taking a mixed shape would be big.
We can call from anywhere or we can easily return to group 1-shanten by drawing one of
many ryanmen.
The turn isn’t too late. From the 10th turn on, it’s good to preserve any kind of shanten,
even if it’s narrow.
Single suit hands (honitsu and chinitsu)
Good cost-performance that can be expensive even open, it’s common to force these when far from
tenpai. That’s why it’s often hard to judge whether to go for single suit or not. In this subsection,
we’ll focus on hands where such a decision is dicult and try to establish some basic rules of thumb.
1.4. YAKU COMPOSITION TECHNIQUES 79
When to commit to single suit
We have at least 10 tiles of the desired suit, including honors that have been cut less
than twice, and at least 4 blocks
We have no groups in another suit Unless a multi-suit hand would be cheap with a bad
shape, and the single suit hand would be expensive and easy to call.
Example werzzxxvvn,... drop manzu
We have at least two strong blocks in the o suits With one o suit block, a single suit
hand can still be made very naturally preserving shanten along the way, but with 2, going for single
suit is often overdoing it.
Example qweruuioooasxc cut u
We’d rather go for junchan sanshoku here, even though we have 10 manzu.
We have another open yaku (especially yakuhai) but less than 3 dora When not going
for single suit gives at least 3900 or mangan, not going for it is common, but we still should if speed
isn’t aected too much.
22
Example 6th turn, dora g
rtdfgghjkl155
5
Since we get 3900 without single suit, cutting 1 is good. But when we draw d or h later,
we’d have to cut dora for 2000 tenpai, so at that point we’d revert to haneman iishanten by cutting
from manzu. If the manzu were a bad shape, we’d drop them immediately in the example situation.
If a hand satises all four of these criteria, going for single suit mainline is no problem, and
we should call everything to advance. (Except in hands like qwerttyuui444
which are very wide and would be too cheap open.)
However, these criteria are for committing to single suit. If the hand doesn’t satisfy one of
them, we should still play with an eye for single suit, hoping for good draws. How much to go for
single suit in hands like that is more dicult. Let’s call a hand state that can commit to single suit
A, and a hand state that can safely ignore single suit B.
Consider the relative ease of achieving A and B
When we have many tiles of the single suit and one o suit joint, we get to B when we tsumo
into the osuit joint, and we get to A when we tsumo or call into any other block, which will
also create a callable shape that can advance faster. In this kind of case, A will usually be much
easier to achieve than B, and it will often be good to drop the the o suit joint while holding on
to single suit oating tiles and live honors, calling into a single suit even without sucient blocks.
In a hand where the relative chances are more equal, it’s often good to cut isolated honors without
overcommitting to either A or B.
22
To quote zeRo さん: if we have a yakuhai pair, we should always take 2 seconds to think about honitsu.
80 CHAPTER 1. TILE EFFICIENCY
While the relative ease of A and B depends a great deal on the shape of the numerous suit, what
many players fail to realize is that it also depends greatly on the shape of the osuit. Especially in
a bad early game hand, it’s quite common to commit to even an uncertain single suit if no other
yaku are in sight.
Consider the relative strength of A and B
Simply put, this refers to their relative score. With 2 yakuhai pairs (or 1 yakuhai pair and 2 or 3
single yakuhai) or when holding a dora or aka in the single suit, it’s easy to make mangan and we
should call even more aggressively. On the other hand, when we already can make mangan even
without single suit, or when we have an osuit dora or aka, it’s best to go for yakuhai + α and
maybe single suit if we get good tsumos. We should especially keep single yakuhai when going for
single suit is realistic.
Example West seat, 2nd turn
yhllcbbn,22445 cut y or h
Honitsu mainline, with toitoi as a backup plan. It’ll probably end up as honitsu only 2600 but
since it’s dicult to win otherwise we can’t help it.
Example 4th turn
etuaadffgj1337 drop manzu
If we can make one more block in pinzu or honors, we’re set.
Example 6th turn
yassdfghjjlbn6 cut 6
We have 10 pinzu, but drawing onto the osuit is realistic and we can make other yaku, so we
don’t commit.
Example 1st turn
qwfhkxcbbm,567 cut qw
Choosing between yakuhai and penchan. If we can stack yakuhai, we can see mangan, so we
want to keep this option open.
Example 8th turn
wesdhk,,135577 cut we
We have enough blocks for honitsu mangan, and we can also make toitoi mangan. Because it’s
a late turn, we shouldn’t overcommit to either, but depending on the progress of the opponents we
can settle for 1000 or 2000.
Single suit hands are powerful, but they are also easy to read for opponents. However, it’s best
not to worry about this too much. Making an expensive hand without opponents noticing is rare,
while going for a single suit when the hand is bad can scare opponents and is actually an advantage.
However, when we have completed the blocks for the single suit, it can be good to cut honors and
tiles from the single suit to camouage. Also, when committing to single suit, it can be good to
discard tiles from the second most numerous suit rst to make opponents uncertain about which
suit we’re aiming for, making it slightly easier to call.
Example yxcbm,11133
5
55 cut b
1.4. YAKU COMPOSITION TECHNIQUES 81
Since single suit hands often give rise to many-sided waits, it’s good to know these (see subsection
on many-sided waits). http://hinakin.main.jp/mckonweb/index.htm is also a good trainer for
chinitsu (warning: 20 second timer, HARD).
Mahjong veterans’ single suit criteria
Though we’ve discussed some criteria of single suit commitment judgment, there will be many cases
in actual play where deciding will be dicult, and play styles will dier even among strong players.
We have therefore chosen to include the following blog posts (needs an account to view) by チルノ
さん and 氷室さん.
From チルノさん’s 幽雅に咲かせ、無理染めの桜”:
23
I’m not really a single suit kind of player, but I’ll try to nd out the border of life of single suit,
with normal hands in an equal point situation. In all examples, assume East round, South seat,
2nd turn, all yakuhai live.
2 yakuhai pairs and up (see blog for other hands, I might translate this in the far future)
Example rio
9999999
5577
If the other suits are all bad shape, this is about the border. If the isolated honors are dead, I
have an osuit ryanmen or a dora-related joint etc. I’d ignore single suit. Haipai with 2 yakuhai
pairs usually means going for honitsu or toitoi.
Example wryi
999999
5577
Even with an osuit ryanmen or dora-related bad shape, this is about the border of single suit.
If I have an osuit group or several good shapes, I’d try to balance.
For example:
Example riodgzxx135577dora j cut z
This could well become toitoi, but start with z.
Example riogjzxx135577dora j cut 3
Comest mangan is when we draw a second j. The z feels useless but I’ll start with honors.
Example rioassbn135577dora j 2000 is ne I guess
Example rioasvb1235577dora j cut as
Maybe won’t honitsu but starting with as has a good feel.
Example riosgjvn135577dora b normal mode
Example wriosfvb135577dora m cut sI guess
Example wruissvb135577dora m cut vb?
23
Let them bloom nobly, the cherry blossoms of forced honitsu
82 CHAPTER 1. TILE EFFICIENCY
Example wriossfvb35577dora m perhaps not single suit
Example rtuuiossvb5577dora m cut s
Might drop s here, but it’s hard...
Example wriossf,.35577dora m honitsu looks good
Example wriosscbm35577dora m not in manzu
Maybe in souzu though.
Example wriosfjl135577dora m look at discards
Probably look at discards and see which honitsu looks easier to make.
Example qtu
9999999
5577
Toitoi or honitsu with a pair from a dierent suit looks better, doesn’t it?
Example rt
99999999
5577
Looks like something else will stick before honitsu.
For example:
Example qtusgcc1345577dora z cut q
Example qtusgcc1345577dora i sketchy
Example qtusgcc1345577dora e cut s
Example wtudhcc1345577dora m cut w
Example wtudhcc1345577dora i sketchy
Example wtudhcc1345577dora e cut h
Example wtuahcc1345577dora a start with h?
Example rtdhcc13465577dora j cut d
Example rtfhcc13465577dora m sketchy, doesn’t look like
honitsu
Example rtghcc13465577dora y doesn’t look like honitsu
Example rtghzc13465577dora y nope
Example rtfhzc13465577dora y cutting z feels okay
Example ryu
9999999
5577dora r
With one more dora this gets good enough so don’t want to force too much. Yakuhai 3 dora 1
also exists so single yakuhai become important.
1.4. YAKU COMPOSITION TECHNIQUES 83
Example ryudgjzx135577dora r
This is still zx but
Example ryuggxc1235577dora r
Example ryuggjvn135577dora r
hands like these are 3.
Example wryuggjv,15577dora r
Don’t commit to honitsu but cut ,.
Example ryuiggjv,15577dora r
Same but still ,v1.
From 氷室’s blog:
1. When the dora is an honor or in the suit we’re considering Honitsu suddenly becomes
much stronger, and getting 3900–8000 is easy. Being aggressive and making the opponents
wary is not bad. Even with a riichi to the face, holding out with some honor tiles is common.
(By the way, when the pressure is strong like this, opponents won’t riichi shitty hands, so you
should pay attention.)
2. When a closed advance would give a shitty wait for 1300–2600 but honitsu might
give 2000–5200 The so-called forced honitsu from a shit hand. Honitsu stacks easily with
other yaku, and can be freely called so it will even complete once in a while :^) However, with
a bad haipai, 1000–2000 yakuhai isn’t bad at all. There are many players who try to force
honitsu to the bitter end without considering clearly faster opponents or the wider situation.
The same can be said about defense. Being no-ten with a 2000 honitsu with 3 calls down
should be avoided Especially when opponents can obviously see how cheap the hand is.
3. When we have 2 yakuhai (or 1 yakuhai and some live honors) Gotta go for honitsu,
toitoi, dora and so on for at least 3900–8000. Getting 2000 with the rare double yakuhai
starting hand is a tad wasteful.
4. When we need at least 3900 at any cost, and the hand is shit This occasionally
happens in all last, and forcing honitsu there is quite good. (For some reason many people
hesitate to do this.) With a shit hand, getting 3900 closed is hard :^)
And here are some special traits of my own style of going for honitsu:
1. Focus on score over shape This might be unexpected, but I don’t care that much about
how many tiles of the suit I have. Of course, that’s doesn’t mean I don’t think about it at
all... How high can I score with honitsu? How high can I score without honitsu? are more
important questions when I’m deciding.
84 CHAPTER 1. TILE EFFICIENCY
2. Play condently When going honitsu is clearly better, it’s normal to drop osuit tiles and
keep single honors. This isn’t really a special trait... but when spectating I see a lot of people
who undervalue single honors.
3. Floating honors This ties in with the previous point, but when holding several of them,
I often think of what the shape will look like when one of them pairs up. This isn’t really
supported by statistics or anything, but with 3 of them drawing a pair happens pretty often.
4. When the shape or score is meh, don’t overcall and keep safe tiles By the way, this
isn’t just for honitsu. But it’s a pretty dicult skill I guess. You might miss the train, but
you don’t want to get run over by it :^) Especially with forced toitoi it’s even easier to die.
Chanta, junchan, honroutou
Similar to single suit in that it restricts the entire hand, but harder to make and worth less points.
With a yakuhai pair and no dora going for honitsu gives 3900 or 5200, but with chanta it’s only
2000 or 2600, which is a big dierence. There will be many cases where a cheap hand which can be
won comfortably will sacrice speed for honitsu, but rather than going for chanta it’s often better
to go for yakuhai only. The value of chanta only becomes apparent in mangan-class hands like
yakuhai chanta dora 2 or junchan sanshoku dora.
That being said, if winning closed looks unrealistic, and we can go for a reasonable open chanta,
we should. In general, go for chanta when we have at least 4 blocks. We shouldn’t restrict
ourselves to a closed hand, but call from anywhere.
Chanta is easy to combine with sanshoku, and there will also be many cases where we can go
for either chanta or ittsuu. The idea for comparing the two alternatives is similar to comparing
sanshoku and ittsuu (see above).
Example East round, South seat, 8th turn, dora .
weadfhjklm,.44 cut h
Going for chanta/pinfu good shape over ittsuu bad shape, this is a fairly straightforward prob-
lem.
Honroutou can often be made by upgrading a chanta or toitoi, so it’s not very important to pay
attention to it specically.
Example 1st turn, dora 4, 3 is a guest wind
qeyiadjlxvm.33 cut y or v
We’ve treated this example before. We cut yor v (to preserve sanshoku) and call everything.
If in the West seat, we cut the same tiles to begin, but don’t force chanta, going for West only and
maybe chanta.
Example 1st turn, dora 4
qeyuasjlcvm.44 cut y or v
Even with ryanmen we still go for open chanta. But in the West seat, it’s faster to drop as
and go for yakuhai.
1.4. YAKU COMPOSITION TECHNIQUES 85
Example 5th turn, dora s
qqeuoasdxcnm.. cut n
At this stage, riichi is not dicult and junchan isn’t conrmed, but we can call anything except
v. While the loss on drawing v hurts, on drawing anything else next going for junchan is both
faster and more expensive.
Sanankou
While it can be scored with an open hand, it’s a closed yaku in practice as the 3 sets must be
entirely self-drawn. As it’s dicult to make and undervalued at 2 han, the necessity of being aware
of it is low.
Example wwuiossflllvvn cut f with no dora, else v
With a mediocre no yaku no dora hand, we should preserve the weak 3 pair shape if it can make
sanankou. With any yaku or dora, or if vvn were vvb, it’s good to cut v.
Example rtyyyuukkzzzcv cut r
While u is widest, preserving iipeikou and sanankou gives a big dierence in value. If we have
two closed sets before tenpai, it’s indeed good to be aware of sanankou.
While comrmed sanankou can sometimes be upgraded to suuankou, if we have no other dora
or yaku, the riichi increase from 3200 to 6400 is very big and the standard move is instant riichi.
With dama 6400 we can wait for an upgrade.
Kokushi musou
With the exception of the coincidental yaku tenhou and chiihou, all the other yakuman except
kokushi musou can be made by upgrading a normal hand (daisangen from shousangen, chuuren
from closed chinitsu, the rest from honitsu or toitoi). Since we can aim for these yakuman by going
for a lower hand and crossing over into them if we get lucky and draw the right tiles, and their
appearance rate is extremely low, we won’t explain any related techniques separately.
However, since kokushi musou requires us to completely give up any option of another hand,
we’ll consider it shortly even though it’s rare.
Should we declare a draw?
Simulation results for kokushi chasing
Starting hand draw rate win rate deal-in rate opponent tsumo rate
13 types, 13 tiles 0% 99.812% 0.057% 0.048%
12 types, 13 tiles 2.834% 66.542% 10.637% 9.859%
12 types, 12 tiles 3.797% 55.718% 14.052% 13.162%
11 types, 12 tiles 11.049% 20.960% 23.977% 22.067%
11 types, 11 tiles 11.074% 19.749% 24.525% 22.381%
10 types, 11 tiles 15.024% 6.464% 27.919% 25.453%
86 CHAPTER 1. TILE EFFICIENCY
From these stats, we see clearly that going for kokushi from 11 is good. From 10, it’s
sketchy. From 9, declaring a draw is usually good. Of course, this depends on the situation,
but even when safe from last place by mangan tsumo, declaring a draw from 9 is usually better.
When the scores are especially close, it can be good to declare a draw from 10, even when trailing.
If a hand with 9 honors and terminals looks reasonably winnable as yakuhai, honitsu, chanta,
honroutou etc. for about mangan, we can continue, taking these yaku as mainline unless we draw
the 10th tile for kokushi very quickly. With multiple yakuhai pairs, it’s dicult to commit to
cutting a middle tile, so it’s better to ignore kokushi and call from anywhere for yakuhai 2 + α.
When going for kokushi mainline, it’s ideal to keep a backup plan with one of the above yaku or
chiitoitsu for when one of the necessary tiles dies, but it’s often not possible to preserve this option.
Unless we can go for another yaku early on, it’s better to go for kokushi.
Example quzzxxc.123456 cut u
When committing to kokushi, we cut the most dangerous tiles rst, holding on to safe tiles. Since
opponents will be able to notice the kokushi no matter what, we usually don’t worry about disguise,
but when starting with 10 types, 12 tiles, we can cut an unneeded tile early on to camouage.
Nagashi mangan
The opposite of kokushi. When we have many honors and terminals, going for kokushi is usually
better from a score and defense view, and we’ll usually only consider nagashi in the late game when
going for a normal hand but getting all bad draws. When we have enough honors and terminals for
guaranteed nagashi, we should go for the win even if they are dangerous towards an opponent in
tenpai. This is because a guaranteed nagashi mangan has a higher win rate than even a very good
wait. If an opponent is going for nagashi, we shouldn’t forget to call and break it up. Similarly,
when committing to nagashi ourselves, we should cut the easier to call tiles rst.
Dora in closed hands
Dora is amazing for value, and unless we need to emphasize speed in a situation where score doesn’t
matter, or when defense is especially important, we usually only want to cut dora close to tenpai.
Of course, any blocks and oating tiles that can integrate dora become more valuable.
Since the value of dora depends greatly on the rest of the hand (if the hand is already mangan,
the added value of dora is low, if we have conrmed tanyao, a terminal dora becomes fairly useless
etc.), comparing dora to other components is very dicult. It’s easy to make a WWYD problem
by taking the most ecient discard and turning it into the dora. We’ll leave the more dicult
problems (1–2-shanten eciency) for later and focus here on the easier to compare cases.
Comparing components of the same class
Assuming at most one other dora and at most pinfu as yaku, so each dora doubles the score
Sliding sequences
With dora w, we should cut y from erty to accept the dora.
1.4. YAKU COMPOSITION TECHNIQUES 87
Ryanmen
We should of course keep dora ryanmen. Since there are 4 omote dora but only 1 aka dora, we
should prefer a dora-accepting ryanmen to an aka-accepting one.
At 1-shanten, we commonly break up the overlap in eryufg, but if t is dora and we
have no other dora or yaku except pinfu, we can sometimes break up fg and aim for pinfu dora
2. The dierence in tile acceptance is only 4 tiles, but the dierence in score is very large. (With
1 han elsewhere, it’s better to go for speed taking riichi, tsumo, ura dora into account.)
Bad shape joints
If the dierence is only 1 han, we prefer a ryanmen. When comparing bad shape joints to each
other, the ones with dora are much more preferable, and the 1 han dierence is far more important
than the subtle variations in shape that we discussed earlier. With an overlap into dora, we should
remove it unless we have no other dora or yaku as above.
Complex joints
We usually prefer to x into the shape with the most dora, even if inecient.
Isolated tiles
Being able to draw a second dora for a dora pair is far stronger than being able to make a ryanmen.
Of course, being able to make a dora ryanmen is also very good. In the general ranking of isolated
tiles based on ease of making ryanmen, which is honors and terminals < 2·8 < middle tile < serial
shape, an isolated dora is one rank higher.
While dora neighbors are also stronger, it’s not enough to rank them up against more ecient
tiles. (Because a ryanmen is better than a bad shape with dora. But when comparing tiles of the
same class, we especially prefer those next to the dora.) Of course, 1 tile away from dora > 2
tiles away from dora.
When holding the dora, the tiles 3 away (dora suji) becomes less valuable. After cutting w
from wp and drawing e, the loss is smaller. It’s not 1 rank worse, but from qts; it’s
about bad enough to cut s. The tile 4 away also becomes slightly weaker, as making a ryankan
with the dora at one side is not as advantageous. We cut a from qta;.
But when we don’t have the dora, the dora suji becomes more valuable. With dora r, we
should cut q from qa. If we cut q, we might draw w or e next, cut them, and draw dora
later. It’s a very subtle dierence, but worth paying attention to since it’s easy to discard the dora
suji thinking it will become dangerous in the future.
Dora in open hands
If we have already conrmed an open yaku which can’t use the dora, we should of course get rid of
it rst, since it will be dangerous in the late game. But if we can draw in the vicinity of the dora to
88 CHAPTER 1. TILE EFFICIENCY
create a good closed hand or a dierent yaku, we should hold on to it by cutting a less useful tile
rst. In open hands, dora is even more important than in open hands for the following reasons:
Open hands have more control over completing groups than closed hands, so it’s
easier to use dora.
Closed hands can use riichi, menzen tsumo, ippatsu, ura dora to score high with-
out really paying close attention to it, while open hands can’t use these yaku,
making dora relatively more valuable.
Yakuhai 2 becomes 8000 with honitsu or dora 2, quadrupling value. On the other hand, pinfu
riichi has the same face value of 2000, but with tsumo, ippatsu and ura actually averages around
3500. Adding sanshoku or dora 2 to it only increases average value to 9000, which is only by a
factor of 2.5, and adding value is also more dicult than with an open hand. The dierence is big.
There are many players who don’t realize this and play with a xed image of closed = big win,
open = cheap and quick. There are many hands where this will be true, but from the viewpoint
of expected value, it’s often important to emphasize dora and yaku with an open hand.
Please remember this.
An isolated dora becomes especially good when we have a yaku and enough blocks, allowing
us to stack dora or aim for dora tanki tenpai. This is extremely good for both speed and score.
(Especially when we have exactly 2 han elsewhere.)
Example weruajjkv/466dora a
With a hand like this, it’s good to call from anywhere, aiming for a mangan tenpai like the
below. While this hand has trouble defending, it’s not that bad to push against an opponent’s
riichi, so emphasizing speed is no problem.
Example wera
c
v/66
6
j
j
jdora a
Example psddhkxxv,,.4dora t
With a hand like this we should call anything for open tanyao.
Example p
x
xx,,
,
f
sd
j
hkdora t
This is indeed a bit overkill, but making a sequence in manzu and drawing another aka is another
way to mangan.
Atoatozuke
With conrmed yaku and enough blocks, we should usually call anything unless we’re condent in
a better draw (depending on the turn and the speed of the opponents). With no conrmed yaku,
it’s still often good to conrm a group and try to create yaku later on (atozuke). We’ve talked
about these, but there’s a surprising number of cases where calling is good.
For example, if we have only a single yakuhai, we can still consider calling to complete a group
and try to draw a yakuhai pair later. Since this kind of calling is for an even less conrmed yaku
than atozuke, we call it atoatozuke.
Of course, atoatozuke is not a good idea as often as atozuke. We can say it’s eective in the
following kind of cases:
1.4. YAKU COMPOSITION TECHNIQUES 89
The hand is slow and a closed tenpai would be very dicult. (With a reasonable riichi
hand, calling like this would only make the hand harder to win.)
The completion degree of yaku is low, but we can see multiple possible yaku to oset
this.
Close 2nd in all last, a hand with dora 2 etc. where winning is guaranteed to be high
scoring or wining is especially important.
For possible yaku, we need to see at least 3 or 4. We also want to avoid moves or calls that
make some of these yaku become mutually exclusive (especially with open tanyao). Also, since the
actual chance of winning is low, we should remember to consider defense from the mid game on.
Concretely, we mean the following kind of yaku:
Yakuhai (1 yaku for each single yakuhai)
Tanyao
Single suit (with 3 blocks)
Toitoi (with 3 pairs)
Chanta (with 3 blocks)
Sanshoku (needs 2 more tiles to conrm)
Ittsuu (ditto)
All of these examples are starting hands.
Example qwryiagllvn57 chii t, cut a
Ittsuu, 456 sanshoku, yakuhai.
Example epooc/agkl567 chii rv, cut a
345 sanshoku, tanyao, yakuhai.
Example tiaadgjkm,..5 chii l., cut t
Junchan, 789 sanshoku, ittsuu, yakuhai.
Example (2 is a guest wind)
qqwyooxn.2256 pon qo2, cut n
Honitsu mainline and toitoi, chanta, honroutou, yakuhai atoatozuke.
Formal tenpai
Since no-ten payments exist, it’s sometimes good to call even with no yaku (formal tenpai, keiten).
If opponents aren’t explicitly attacking, call from a good shape 1-shanten with about 16
tiles left and from a bad 1-shanten with about 20 tiles left is a good criterion. When tenpai
is especially important, like when trailing badly in the dealer seat with a bad hand, it’s good to
call into keiten even earlier, but when no-ten payments wouldn’t change placement but winning
90 CHAPTER 1. TILE EFFICIENCY
would, it’s good to try and win to the bitter end. Situations also exist where going for keiten with
an upgrade to yaku is possible, and we should also call a bit earlier then.
In keiten, we can’t win except for haitei, but we can still deal in, so we want the least amount
of draws possible. Just before a draw, we should call if it allows us to avoid drawing a tile while
keeping tile and dealing a safe tile.
24
In the next section, we’ll approach tile eciency from yet another perspective, centering on
complicated hands, especially those in 1-shanten.
1.5 Iishanten eciency
The importance of being rst to tenpai
The diculty of comparing two alternatives of diering natures
When deciding between a ryanmen and a kanchan, it’s always better to choose the ryanmen unless
there’s something special going on, so that there’s nothing to hesitate about. The reason is that
when comparing things of the same nature (joints), we can decide based on tile acceptance alone.
25
Conversely, we only waver when comparing two alternatives which dier by their very nature.
In mahjong, there are two great choices between things of a dierent nature. The rst is
between value (yaku and dora) and speed (tile acceptance, wait quality). The second is between
hand components of dierent types (isolated tiles versus extra tiles in complex joints etc.). Though
we have discussed both of these comparisons to some degree, when these factors enter the equation
in a more complicated way, things can get very dicult. It’s especially troublesome to choose the
correct discard when there are many eective tiles.
Luckily, we can often deal with hands that are far from tenpai by applying the rules that
have been briey discussed until now about comparing isolated tiles and joints depending on their
surroundings and the rest of the hand. The need for complicated comparisons is restricted to 1–2-
shanten hands. As we will see, there is a limited amount of possible iishanten types that will make
it easier to systematize this kind of decisions. (That being said, 2-shanten will be the stage where
we’ll most often have problems deciding.)
The advantage of head start tenpai
While we’ve already pointed out that emphasizing tile acceptance close to tenpai is a fundamental
rule, this is because being in tenpai (especially as the rst player) is a big advantage. Formerly,
strategies that put the most emphasis on tile acceptance when in tenpai, that is wait quality, were
the mainstream. The reason this strategy has changed is the following.
Until a few years ago,
26
getting into tenpai with a good shape (ryanmen or better) was considered
especially important. This tendency can even be felt in Totsugeki Tōhoku’s older posts. Since the
step from tenpai to winning on average takes the most time of all, it was thought that aiming for a
good shape tenpai even at the expense of tenpai speed increases win rate. This is also the reason
why bad shape riichi was often unfairly undervalued.
24
This is a simplied presentation of a very dicult subject. Entire books could be written about formal tenpai
(look up 形テンの極意 by ASAPIN).
25
In general, things of the same nature have the same qualities but in diering degrees insofar as they are similar,
making it easy to choose that alternative which exhibits their common desirable qualities to a greater degree.
26
roughly 2000–2005
1.5. IISHANTEN EFFICIENCY 91
However, because a hand with yaku can win from anywhere (a hand with riichi can be hard
to ron, but by making opponents fold or roll, it increases the time available to win relative to
opponents), the #1 longest step is from closed iishanten to closed tenpai, because we can
only use the tiles we draw. (The actual win rate of bad shape riichi was also shown to be not that
bad by statistical analysis.)
Accordingly, the strategy of maximizing tile acceptance at iishanten and instantly call-
ing riichi even with a bad wait has recently become mainstream.
Of course, there are hands where it’s better to prefer making a good end shape in iishanten.
Together with the trade-o between speed and value, hands like these will form the subject of this
section.
Example qweydffglllb44
This hand is widest on cutting f (3 tiles more compared to y and b), but in practice this
is never played, preferring the higher chance of a good shape and the score from possible iipeikou.
Classication of iishanten
These are the basic types of iishanten. Since they dier by their inherent nature and have dierent
advantages and disadvantages, it’s often dicult to decide which of them to go for when several
are available. For this reason, it’s important to be aware of each of these patterns to be able to
recognize them quickly.
27
(1) 2 groups, 2 joints, 1 head: extra tile shape
Example qwesdjkcvb..4
Characteristics: since the extra tile doesn’t directly contribute to tile acceptance, the total tile
acceptance is often low. However, the extra tile can be used as a safe tile, or to upgrade into a joint
that makes for a more valuable hand.
(2) 2 groups, 1 complex joint, 1 simple joint, 1 head: no extra tile shape
Example qwessdjkcvb..
This shape consisting of a ryanmen and a ryanmen pair is called perfect iishanten.
Example qwedddfjkcvbn
This shape with a many-sided wait is also considered to fall under (2).
Characteristics: often wider than (1). Only hands like the second example can end up with a
many-sided wait that isn’t sanmenchan.
(3) 3 groups, 2 joints (or 1 joint and 2 isolated tiles), no head: headless shape
Example qweasdjkcvbm,
27
For a gentle introduction to the subject, see https://youtu.be/mKEOEWEc5JE (EN subs available)
92 CHAPTER 1. TILE EFFICIENCY
This shape has 2 joints, but the weaker shape with j3 instead of jk also belongs in this
class.
Characteristics: since we can get into tenpai when one of the joints turns into a group or into
the head, it’s wider than (2) if we have 2 joints. However, if we don’t have a serial shape or closed
set, we get a tanki bad shape if we draw a group.
Example qweasdjk333m,
This shape is called the anko headless. When we complete a ryanmen, we can downgrade the
closed set into the head and end up with the other ryanmen as the end shape. Please remember
this very strong shape.
(4) 3 groups, 0 joints, 1 head, 2 isolated tiles: sticky shape
Example qweasdjcvbm..
Characteristics: since turning an isolated tile into a joint is much easier than turning a joint
into a group, this shape is the widest of all. However, it can be easy to get a bad wait, unless we
have a serial shape.
(5) 5 pairs: chiitoitsu iishanten
(6) Combination of (5) and (1) or (2)
(7) Kokushi musou iishanten
For these, see the subsections on chiitoitsu
28
and kokushi musou.
Quantitative comparison of classes
Table of tile acceptances for common iishanten shapes
acceptance into good end shape/total acceptance
iishanten class 2× bad bad + good 2× good good + ultra good
extra tile 0/8 4/12 16/16 19/19
perfect 0/12 4/16 or 8/16 20/20 23/23
headless 0/20 6/24 12/28 26/37
anko headless 0/20 10/24 28/28 37/37
honor terminal 2 or 8 middle 3445 3456
sticky 0/4 0/12 4/16 8/20 14/17 14/29
Includes half the 0/2 acceptance for drawing a set from the pair, so just take the sum of the two
isolated tiles, for example qwertyuusm accepts 4/16 + 8/20 = 12/36 tiles.
29
28
The material on chiitoi in this book is quite thin. I’ll try to remedy this once I’m done.
29
This table wasn’t present in the original, I hope this will convince people more clearly that wider shapes are in
fact strong and by how much
1.5. IISHANTEN EFFICIENCY 93
Extra tile shape
In a shape with 2 groups, 1 head and 3 joints, we have to decide which joint to break. As discussed
before, we should use the criteria for comparing joints. If there is no dierence in tile acceptance
or value, we should drop the joint whose backres have an overlap.
Example qwetysshjxcvbnm cut y
Drawing r upgrades the hand to tanyao.
However, when comparing simple joints in 1-shanten, there’s one thing to keep in mind. Al-
though more central joints have more upgrades, more outside joints are easier to win with, so we
need to balance the relative frequency of cases where we draw an upgrade and those where we
complete a group. When comparing an outer and inner kanchan, the win rate disparity is not that
big, so we should prefer the inner kanchan’s double upgrade. But when comparing a pair of 2s
and a pair of honors, the latter is signicantly easier to win with, so we’ll usually prefer it. The
opponents’ discards also play a large role. When not in 1-shanten, drawing an upgrade will happen
a lot, so we should generally prefer upgrades.
When deciding which extra tile to keep from a situation other than the 6-block one above, we
should keep an extra tile that is most valuable in some way.
What should be kept in mind is that at 1-shanten, an upgrade that overlaps with another wait
can’t be considered an upgrade and we can only perform it by refusing tenpai, so we should ignore
it unless declining tenpai is for some reason very advantageous.
Example yuiooadcbm, drop cb
While the cb theoretically has more upgrades than ad, drawing n already puts the hand
in tenpai. Accordingly, choosing the easier to win s wait is better.
What to keep as the extra tile
There are several dierent ends towards which the extra tile can be used:
A tile which is useless but serves to confuse opponents (rarely, if no better option is available)
Safe tile
Floating tile to make a ryanmen
Floating tile next to the head (can advance into a wider headless or sticky shape if the sequence
completes)
Tile to create value from yaku or dora
In the early and mid game in a normal situation, the options are ranked from worst to best.
Dealing in with the extra tile doesn’t happen that often so we can emphasize our own hand, and
upgrading to double value is often preferable to upgrading the end shape. When both joints are
already good, keeping a safe tile is better than a tile which creates ryanmen or a tile which can
advance the hand to a wider iishanten class (unless this would be very advantageous somehow). If
tiles that create value appear dangerous from the mid-late game on, we should also get rid of them
94 CHAPTER 1. TILE EFFICIENCY
rst and keep a safe tile. In a shape like wep where the dora can be immediately used to enter
tenpai with a good draw, we usually don’t get rid of it.
With a bad shape, we don’t keep a safe tile. Since the dierence in win rate with an eective
extra tile is signicant, increasing the deal-in rate a little still has better expected value. Since
getting outpaced with a hand like that will usually result in folding completely anyway, dealing in
with the extra tile will happen rarely.
The comparison of extra tiles can be done using the material discussed above. (When keeping
a safe tile, keep the safest one, or one that’s safe against a player we especially don’t want to deal
into from a points standing perspective.) It’s easy to disregard this kind of comparison as opposed
to comparison of joints, so we should pay attention to this.
Example yuoosdhjkll... dora 4 cut h
The three options which preserve the shape are ohl. Cutting o has no added benet.
Cutting l helps create ittsuu with g, but cutting h and aiming for junchan is best, with an
upgrade on any of jkl. While it returns to a bad shape and the yaku isn’t conrmed, with a
potential mangan it’s better than a ryanmen riichi only.
Ukase-uchi
In a shape with 2 groups, 2 joints and 2 pairs (14 tiles total), it’s usually best to break up a bad
shape joint, or to break up a pair if both joints are ryanmen. When deciding which pair to break
up, there is an opportunity for ukase-uchi, breaking one pair into a oating tile with upgrades into
better ryanmen than the hand already has. Otherwise, it’s best to emphasize safety.
Example eertysdghjccbn cut e
Can draw a sanmenchan or a ryanmen that conrms tanyao.
Example rtuioaadfgvvm, cut v
The oating v can be used to make sanshoku.
Example werttkkxcbnnm, cut t
Aiming to create a sanmenchan or non-overlapping ryanmen.
Example tyaahjccnm,555dora x cut c
Can draw a dora ryanmen. We can also cut a if we suspect c would be too dangerous later
on.
Perfect iishanten
The basic idea when comparing dierent perfect iishanten is to compare the complex joints, focusing
on xing those that have good shape and xing shapes that create value. When there’s no big
dierence, we should emphasize an easy to win (on the outside) end wait.
Example wwessjklvvb
7
77 cut w
1.5. IISHANTEN EFFICIENCY 95
While the qr is easier to win with than cn, the w is easier to call pon on than v.
While this is a dicult decision that is inuenced by the table situation, xing the good end wait is
usually better. Though this is in contradiction with the iishanten peak theory discussed earlier, the
improvement to the win rate from tenpai is more important here than the improvement to tenpai
rate.
The fact that makes iishanten peak theory work is that winning is possible from any player,
while entering closed tenpai requires a good tsumo. (There is also the advantage of riichi pressuring
opponents to fold) With closed perfect iishanten, the eective acceptance a is 20 tiles from 1-shanten
to tenpai, and b = 4×8 = 32 (slightly lower in practice) from tenpai to win. Since the expected
number of draws from 1-shanten to tenpai is 1/a and the expected number of discards from tenpai
to a win is 1/b, a marginal improvement in a is more valuable than one in b when a < b. However,
with a wider class of iishanten, a b, and iishanten peak theory no longer works as well. Similarly,
for an open perfect iishanten, a = 4×4+2×16 = 48 while b is still only 4×8 = 32, making iishanten
peak theory unreliable.
30
Extra tile versus perfect iishanten
Since perfect iishanten is wider, when there’s no specic reason it’s simply better. For the same
reason, a headless or sticky iishanten is better than a perfect one.
Don’t break perfect iishanten to keep a safe tile
The dierence in win rate is too large to justify a small reduction in deal in rate. This move
only makes sense in hands like errooxc4 where e is dora and eo have been cut
twice.
In the following examples we’ll mostly consider 2-shanten with 2 groups, 1 head, 1 complex
joint, 1 simple joint and 1 oating tile, with the option to take either an extra tile iishanten by
cutting a tile from the complex joint, a perfect iishanten by cutting the oating tile, or to stay in
2-shanten by doing something else. In all hands, assume East 1, 7th turn, dora 4. From the 11th
turn on, it’s usually better to take perfect iishanten, considering no-ten payments.
When the good shape is complex
Example weruggklzxcm,, cut u
Sacricing 4 tiles of immediate tiles acceptance for 8 tiles worth of ryanmen upgrade isn’t worth
it. However, if any of yuiowere dora, it’s good to cut ,, since there would be many upgrades
for better value. However, with no dora, we should also cut , if we want to avoid a riichi only
with a bad wait. When playing with aka dora, this is often the case.
Example weruaafhzxcm,, cut u
Here the inner kanchan has the same amount of ryanmen upgrades as the oating tile, so it’s
clearly better.
Example wertggklzxcm,, cut ,
30
Paragraph added by me to explain this fact more clearly.
96 CHAPTER 1. TILE EFFICIENCY
But here, there are 14 tiles for upgrade into ryanmen versus 4 tiles of immediate acceptance,
so , is good. If gg were hh, we would consider cutting l and returning to 2-shanten with
better shape.
Example werfggklzxcm,, cut ,
The oating tile next to the head is very strong, allowing us to make a good shape with any of
dgkl.
Example weruggllzxcm,, cut ,
The immediate loss in tile acceptance is only 2 tiles, while the amount of upgrades is very high.
This is a typical example of the theory that breaking up a 3rd pair is good.
Example wertfhllzxcm,, cut t or ,
Even on cutting t, there are still 8 tiles of upgrade to ryanmen. The dierence is subtle and
either of t and , can be good.
Example wertggklzxc,.. cut l
Here, we think the return to 2-shanten with l is strong. This play is generally good in the
following kind of cases:
1. Advancing shanten makes a cheap hand with a bad wait likely
2. There are many tiles that revive the hand into a better 1-shanten (qerygm. in the
example)
3. It’s still the early game (6th turn or earlier)
When there is a possibility to upgrade into a better shape even when advancing, the criteria
become stricter. On the other hand, if the upgrades don’t just improve the wait, but also increase
value, they become looser. Furthermore, in the above example cutting , or . as a kind of
compromise is not a good plan, since a cheap hand with a bad wait remains likely if the manzu fail
to extend.
Example wertggkkzxc,.. cut k
This hand is even narrower than the previous example, so declining 1-shanten is also good.
Example werggkklzxc,.. cut l
While taking the 3 pair shape and hoping to draw f or h is good, cutting g is also playable.
Example qweyuuasdklxvn cut y
While this straightforward move into 1-shanten makes a cheap bad wait hand very likely, cutting
u into 2-shanten has very little promising upgrades and we would most likely end up with an
equally bad hand anyway.
1.5. IISHANTEN EFFICIENCY 97
Example ertysdfhhjbb,. drop ,.
While this is big step backwards in shanten, conrming tanyao creates value and allows us to
call, compensating for the immediate loss in speed. (As mentioned in the subsection on tanyao.)
Example yuusddfkkn,555 cut d
Since we can call pon, the loss from cutting u would be bigger. Since we have a yaku, we can
maximize immediate tile acceptance without waiting for an upgrade.
With a serial shape, a tile next to the head, a middle tile that creates value (or even a non-
middle tile if it’s guaranteed to produce a lot of value) we prefer an extra tile shape. If we want
to avoid a no dora no yaku bad shape riichi, we can keep even a regular middle tile. If the bad
joint has a tile acceptance overlap, breaking it up and returning to 2-shanten is often good (this
depends a lot on the turn, but in the early game we should return). If the bad shape joint is easy
to upgrade, perfect iishanten can be ne. With a 3 pair shape, we can take an extra tile even if it’s
a regular middle tile. But when calling is eective, the loss from not being able to call pon is big,
so we should only refuse perfect iishanten for a big increase in score.
If both our joints are bad, it’s often not a good plan to aim for an upgrade, since even with an
upgrade the end shape will be bad 2/3 of the time (because a good shape is easier to draw). Taking
the perfect iishanten to maximize tile acceptance can’t be helped.
When the bad shape is complex
Example wertasdhjllbm. cut w
Since keeping the complex bad shape joint gives a bigger chance at a good end shape, we prefer
it over a connect 4 shape.
Example wertyuihjllbm. cut .
But the connect 7 shape is so strong we can break up the ryankan (also seeing 567 sanshoku).
Example qqwerdfghcvnn, cut ,
Here, there are also upgrades to tanyao and 234 or 345 sanshoku.
Example qqrtsdfhjjbnnn cut j
The upgrades to a much more expensive (vbmm) hand are big. If n were dora, the value
is ne but we still want these upgrades for calling into open tanyao, so j is still good.
Example ertyaafgvvb... cut v
Here, doubling the probability of sanshoku is big. While it also enables calling, a kata-agari is
not that great so if . were dora, we should cut either of ey.
Example tttyuaahhjzxcn cut h
Since the loss from cutting h is only 2 tiles, chasing even a far-o sanshoku is better. We can
also use the oating n to make pinfu. If we draw another manzu for a complex shape, we should
98 CHAPTER 1. TILE EFFICIENCY
cut n since the dierence in tile acceptance will ber very large.
With hands like these, holding an extra tile is only worth it when it has many upgrades for
better shape and also adds value. However, if an upgrade would double the value, we’ll often try
to preserve it, especially with hands that would only be worth 1300–2600 otherwise. If a hand is
already worth 3900 or more, it’s often best to maximize speed (a 3900 hand with riichi is actually
worth about 6300 on average). Only an upgrade to haneman would be worth sacricing a lot of
speed for, and this is quite rare.
When we have to cut dora
A closed hand with a oating dora that can cut it to make perfect iishanten or keep it for an extra
tile iishanten.
Middle tile dora In a hand worth 2600 without the dora it’s better than a serial shape, in a
hand worth 5200 it’s worse. In hands worth something in between, use discretion.
Dora is 2 or 8 If we can see 5200 and up without it, cutting it is good.
Terminal or guest wind dora Usually cut. If we have no other dora or yaku, we can keep it
depending on the point standing. If any win is ne, we cut it. If we want points, but a riichi only
hand is okay, we hold on to it as an extra tile. If we absolutely must win an expensive hand, we
should return to 2-shanten by breaking up a bad shape joint.
Yakuhai dora The risk of opponents calling it is big. We should especially avoid discarding it
if opponents have made threatening calls. If no such calls have been made, we should cut it with
2600 good shape or 5200 bad shape. With a cheaper hand, we should hold it as an extra tile
unless we don’t care about score. With two bad shapes, discarding a yakuhai dora for such a bad
hand is problematic, so we’ll often return to 2-shanten and aim for riichi with a dora pair or dora
tanki.
Dora at 2-shanten and before
As opposed to 1-shanten, keeping a oating dora while narrowing the shape doesn’t really decrease
win rate that much at 2-shanten. We’ll usually keep it until 1-shanten, and discard it only if
nothing sticks to it and another tile becomes more valuable. Conversely, when choosing between a
2-shanten with an extra tile dora which we would most likely discard anyway later, and a 2-shanten
which would lead to a clearly wider 1-shanten, we should prefer the latter. We mean a hand with
multiple complex joints, none of which we want to break up.
Example ttuuidffghcbnndora c cut n
The loss from holding the dora close is small. (Since we have tanyao, we don’t really care about
losing out on chiitoi.)
Example eeerrtdgjzzcvmdora m cut m
Cutting anything else is too much of a loss.
1.5. IISHANTEN EFFICIENCY 99
Cheap open hands
We mean hands that are worth 1000–2000 without holding on to the dora. Drawing a second dora
is a huge increase in score, but using only one is not as However, it’s easier to make dora tanki
since we can call. For this reason, it doesn’t matter as much as in closed hands how easy it is to
make a sequence with the dora (a dora tanki is easier to win with if the dora is dicult to use). In
these examples, we’ll take dora 4.
Example cvmm,aa4 cut 4
Since the loss from not being able to call pon is big, we cut dora. If we need a big hand, we can
cut m.
Example xvmm,aa4 cut 4
If we need a big hand, drop xv.
Example cvmm.aa4 cut any of 4.a depending on situation
While dora is more important in open hands, the loss from not taking a perfect shape is also
bigger.
Understanding tenpai chance
A not very enlightening theoretical article reiterating many points discussed earlier, including
Since the marginal value of tile acceptance is higher when it’s low, tile acceptance dierences
are less important with wider iishanten.
This makes it more important to emphasize end shape and value.
When comparing speed and value, speed is often more important.
With a wider shape, playing by feel according to circumstances becomes more important
compared to theory.
Not understanding the importance of tile acceptance and not understanding its relativity is
both bad. It’s important to balance these two. But chasing a balanced course for its own
sake without thinking of the optimum course is also foolish. Often, the optimal move will be
extreme while a compromise will be worse.
Headless iishanten
Can either have 1 joint that can complete into the head or into a group or 2 joints. The shape with
2 is much wider so we should almost always prefer it, unless a very good isolated tile is preferable.
Example qqqertfgzxcm.7dora 7 cut .
With 2 aka, cut 7. With 1 aka, use discretion, depending on the point standing.
Example qqqertfgzxcnm7dora 7 cut 7
100 CHAPTER 1. TILE EFFICIENCY
Since the dierence in tenpai chance is very big.
Example qqqertuihj45
5
5 drop hj
The dierence in score is very large.
With a 1 joint shape, we should pay attention to keep the isolated tile which makes it easier to
create a head:
Example qqqifzxcbn,555 cut i!
While the , in bn, is usually weaker than a normal i, this time drawing m creates a
good wait and drawing b also gives tenpai.
Similarly, even before 1-shanten, if we don’t have a head, number tiles in shapes like these
become slightly stronger.
Example rtuuioahklcvbm cut a
But if a more central tile exists that it’s easier to make ryanmen with, we should still prefer it.
Similarly, in a 1 joint headless iishanten, we should prefer a middle tile to a safe tile.
Example errtasdghcvbm4 cut 4
Extra tile versus headless
With a shape like qqwe or qwwe, xing a group can give a headless shape, or xing into
the head can give an extra tile shape. If we have a closed set or a serial shape, we should
prefer the headless shape. This is because they increase the tile acceptance for ending up with
a good wait.
Example qwwesfghjzzznm cut w
Example qwwefghjkzxcnm cut w
Example qwwefgghhzxcnm cut w
Example qwwehjjklzxcnm cut w
Example qwwehhjkkzxcnm cut w
But with a serial shape like qwwee, it’s actually harder than usual to make a head, so
it’s better to x the head.
Example qwwejjkklzxcnm cut e
There is no benet to drawing r so we keep q for safety.
Example erassddghjkcvb cut d
Aiming for tanyao and/or 345 sanshoku. The assdghjk shape completes with any
of fgl.
1.5. IISHANTEN EFFICIENCY 101
Example uuiioasdghjkcv drop cv
Hoping to extend pinzu into a better shape.
Without a serial shape
With all ryanmen and no serial shape, the headless shape has a wider tile acceptance, but the extra
tile shape has a wider tile acceptance towards a good wait. This is a famous shape where it’s easy
to hesitate.
Example qwweasdhjcvbm, cut w or e?
We should decide depending on the discards, choosing the option with more tiles left. If the
hand is too cheap to attack with a bad shape, taking the guaranteed good shape iishanten is
recommended. Keeping an extra tile can also be advantageous for other reasons (see above).
If any of hjm, is dora, dora tanki riichi is not bad, so the headless shape is stronger. If
we have a dora in one of the sequences, we can draw another one and turn it into the head if we
are in the headless shape, so it also becomes slightly stronger.
Example qwweaassddhjm, cut w
With a yaku, tanki riichi is ne.
But if we can make yaku, we should of course prefer that shape:
Example qwwesdfhjcvbm, cut q
Example qwwesdjklzxcbn cut w
With at least one bad shape joint, taking the headless shape is better. If we have a werr
aryanmen shape, we can break up the weak joint to make an extra tile iishanten, hoping to draw
a better shape headless iishanten later. The same can be done with a dffg nakabukure if
the turn is still early. When not in 1-shanten, xing a qwwe shape into a group is usually
good since it’s easy to draw a head elsewhere. The exception is usually only when we would have
to discard dora.
When a shape that would allow us to exploit a headless shape eectively (closed set, serial shape
etc.) exists or upgrading into a headless iishanten would in another way be good, it’s often good to
keep an extra tile next to the head in an extra tile iishanten. Otherwise, it’s better to keep a safe
tile.
Serial shape versus score
Example qweeyudfghjvbn cut q
Acceptance is 19/19 with q versus 26/37 with e. But cutting q conrms tanyao, doubling
score, so it’s better despite being narrower. If we draw r afterwards, we should cut e and go
headless. If the pinzu shape was fghjk, the problem is more dicult. We should still cut
q in the early game or when we need an expensive hand.
102 CHAPTER 1. TILE EFFICIENCY
Example qweedfghjvbnnm cut e
Acceptance is 18/18 with qversus 42/42 (!) with e. With a double serial shape, the dierence
in tile acceptance is overwhelming. Unless we absolutely need at least 3900 to increase placement,
e is better.
Open hands
Example qweeyufgvbn77
7
cut q
Since calling with a headless shape always results in a tanki, taking the extra tile shape is better
here.
Example wryssfgxcv
m
n,scomes don’t call pon
Example wryssfhxcv
m
n,scomes calling pon is playable
Calling pon will increase the tile acceptance in both examples. However, we also give up a
tsumo and make the hand shorter, making it harder to defend. Since in the rst example calling
makes it slightly harder to end up with a good shape, it’s better to not call, while we should at
least consider calling in the second one. If xcv were instead bbb, we should call and cut
w for a clearly better anko headless shape, also being able to stick a ryanmen to b.
Perfect versus headless
We’ll center on hands with a many-sided wait. While the headless shape will be wider, the perfect
shape will have the advantage of leaving a many-sided wait. As always, assume 7th turn in East 1
and dora 4.
Example wwweuiojkxc333 cut e
If we want to keep the 3-sided wait, we’d have to break up either of the ryanmen. We call the
shape on cutting c the xed form, on cutting e the owing form. The tile acceptance for the
owing form is 28, and 22 for the xed form, of which 8 tiles give a 3-sided wait. However, the
dierence in win rate between a 3-sided wait and a 2-sided wait is smaller than between a 2-sided
and a 1-sided wait, so we should simply prefer the tile acceptance.
Example wwweertjkxc333 cut e
Here we have a 4-sided wait, with 24 tiles accepted in the xed form, of which 8 give a 4-sided
end wait. While this is a lot closer than the previous example, a 1/3 chance at getting an improved
end wait is not that great, so the owing form is slightly better.
Example wwwertyjkxc333 drop a ryanmen
Here, the two forms have the same acceptance, but the xed form oers an excellent 5-sided
wait. We should look at the discards and drop the worse ryanmen.
Example wwweuiojlxc333 cut l
1.5. IISHANTEN EFFICIENCY 103
Here, taking the owing form leaves the possibility of a bad wait (10 good/24 total). But cutting
l (we can draw h and cut e then) gives a tile acceptance of 22/22, which is a lot better.
Example wwweuiojlxv333 cut e
The owing form has 0/20 acceptance, the xed form (we cut from the outside, hoping to draw
a ryanmen upgrade, and we prefer to preserve the jl as it has the same amount of upgrades
but is easier to win with) has 4/18 acceptance, with the 4 being for a 3-sided wait. Here also,
emphasizing the end shape is better.
Example wwwruiojlxc333 early game cut l, else r
The owing form has 10/24 acceptance, the xed form 18/18. This is a dicult problem. This
dierence in total tile acceptance is the dierence between an average of 5.5 and 7.5 turns to tenpai.
Especially from the mid game on, this dierence has a big eect, so we should cut l early and r
later.
Example wwweuiojlxcm,. cut e
Here we no longer have a closed set, but cutting e anticipates sanshoku. Since the possible
increase in score is very large and the dierence in speed is smaller than between a ryanmen and a
kanchan, it’s better to aim big. When choosing between the xed form and owing form, choose
the one with acceptance towards a big hand. However, if we already had dora 2, the added
value from sanshoku becomes inecient. With a conrmed mangan, it’s better to emphasize
speed.
Example ertteuiojlxc333 cut l
Similar to the example with wwwrjl above, but the manzu shape is easier to extend.
Example weryisdfhkbnm,dora e cut b
Since breaking a bad shape joint when we have two will often lead to bad wait tenpai anyway,
and the b, wait for 6 tiles is not great, it makes no sense to keep the serial shape. We maximize
tile acceptance and can accept another dora to make 678 sanshoku.
31
In short, if the owing form guarantees a good wait, we should take it unless we miss out on a
very good many-sided wait. Since a 2-sided wait is already good enough from a win rate perspective,
it’s often better to emphasize the speed of getting to tenpai.
However, there is often not a big dierence, so if one option is clearly more expensive, we should
prefer that. We can also use information from discards to emphasize the suits that look easier to
draw or come out from opponents.
Example eeertyufgjklvb cut u
If one of the joints in the owing form would be bad shape, we should prefer the xed form by
a wide margin. However, there are some cases where we can take the owing form if the bad shape
joint creates value or is particularly easy to upgrade. On a late turn, we should also emphasize
pure tile acceptance to get into tenpai as fast as possible.
31
This example feels out of place, yeah
104 CHAPTER 1. TILE EFFICIENCY
Problem East 1, 6th turn, dora x Source: Japan Mahjong Organization
32
weerrttydgcvbb
Tsumogiri b, keeping the widest shape with tanyao and sanshoku. When drawing r or u,
enter provisional tenpai for tanyao and try to improve the wait. When drawing q, ignore tenpai
and tsumogiri.
With two bad shape joints, the reasoning is similar to two good shape joints, taking the xed
form only when the many-sided wait is strong. The same ideas about value and the turn as above
apply.
Sticky iishanten
This shape is the widest of them all, and especially in the late game where raw tile acceptance into
tenpai for no-ten payments is important, we’ll rarely prefe another shape.
When comparing isolated tiles, we should be aware that unlike at pre-1-shanten, we don’t care
about making ryankan, so we should not cut c from euc, but one of the other two since they
overlap.
Example werudfghllzxcm cut u
While usually being able to draw t for an easy to upgrade kanchan is an advantage, here it’s
actually an overlap since we can use it to widen the shape even if we discard u.
Example ertydffxcvbnm, cut y
While d is widest at 35 good/60 total, y gives 39/46. While it’s only 4 tiles of good wait
versus 14 tiles of acceptance, if the hand is this wide, it’s better to emphasize end shape. We can
also see 345 sanshoku.
Example wertyuugghvvbn cut v
While h gives an acceptance of 45, only 20 of those give a good shape. v gives 40 tiles
of which 26 good shape, so it’s even better than in the previous example. We can also see 456
sanshoku. While gcan give both 456 and 567, it reduces tile acceptance to 23/23 and is therefore
not recommended.
Example wertffgxcvb666 cut g
Cutting ggives tile acceptance 30/50, cutting wgives 30/41 which is strictly worse. The cause
is that unlike the examples above, this hand doesn’t have a 3-sided shape like wertyuu
or wertyui. While cutting w appears to give 345 sanshoku, we’d need to get either x
or g together with d, which is rare (7/41).
32
Tsuchida Kōshō-chaired organization that disbanded in 2010
1.5. IISHANTEN EFFICIENCY 105
Example errtyuifggbbnm cut f
This hand also doesn’t have a 3-sided shape. The acceptance with f is 28/41, with b 25/36.
f is clearly better. In general, a nakabukure is dicult to turn into the head, so xing a head is
often good.
Example rrttyyuffghbnn cut u
u gives 23/37, b gives 27/43, f gives 26/38. All of these are super wide and likely to give a
good wait, but the u which conrms iipeikou and enables sanshoku and ryanpeikou is a lot better
for score.
Example weefjklbbnm555 cut f
Better because it’s isolated (23/33 versus 19/41 for w).
To recap what we have seen so far:
3-sided serial shape + 2-sided serial shape + ryanmen pair cut from the 2-sided serial shape
serial shape + isolated tile + ryanmen pair cut isolated tile
2×serial shape + ryanmen pair x pair, even more eective with a kanchan or penchan
pair
The relative strength of serial shapes goes as xcvbnm, > cvbn > cvvb
cvbb
Example errdfghccvbnm, cut c
e gives 25/53, c gives 30/35, g gives 25/40 (exception to the above, since the 3-sided
aryanmen is weaker than a regular 3-sided serial shape). Emphasizing a good wait is better.
Example errddfgccvb555 cut d or c
e gives 20/42, the other two give 23/37. The acceptance into sanshoku is 0 versus 8, into
iipeikou 12 versus 6, so d or c is better. If sanshoku wasn’t possible, e would be better. (A
bad shape conrmed iipekou 5200 is better than good shape 2600.)
Problem dora r (Source: Japan Pro Mahjong Federation)
rtttyufghjbnnm
Answer: n is the widest, making ryanmen tenpai even with fj.
Problem eerpyuvbbnm,,.
Answer: e. While , creates a sticky shape which is wider, it makes it impossible to achieve
tanyao, so w is better. While . is playable, the lost acceptance into riichi with bm, is more
106 CHAPTER 1. TILE EFFICIENCY
valuable than being able to call pon for tanyao. This a rare exception where declining a very wide
sticky shape is better to increase the score, compensating with a strong sanmenchan + complex
ryanmen pair.
33
Perfect versus sticky
We usually prefer the much wider sticky shape, but cases where the perfect shape is preferable do
exist. This is often when a 3-sided wait with a closed set (weee) and a ryanmen pair are in
the hand. If we have a head elsewhere, the isolated tile next to the closed set becomes weak. Often,
while the sticky shape will have more total acceptance, the perfect shape will have more acceptance
towards a good wait.
Example qweudddfjklnmm cut u
Example qwedddfjkkbnm, cut f
The serial shape in souzu makes it easy to get a good shape with a sticky shape. But cutting
k has the advantage of being able to make an extremely wide headless shape when we draw the
backre of vnm..
Example eersdfhjjjxcvb cut e until the mid game
While cutting h is the widest overall, cutting e makes it easier to get tanyao pinfu for a
higher score.
34
Example errtyyydddfnnm cut n
With 2 many-sided waits, preserving them is clearly good (28/28 compared to 22/33 with r).
We usually won’t get sanankou so we ignore it.
Returning to 2-shanten
When to return
Returning to 2-shanten is limited to extra tile or perfect iishanten with bad shapes, or chiitoi
iishanten. (Except for special situations where an expensive hand is required at any cost.) We
should never return to 2-shanten after the 12th turn unless we’re folding, because we can get no-ten
payments even with a very weak hand, unless the point dierences are very large and we don’t care
about no-ten payments.
Patterns of returning
Assume East 1, West seat, dora unrelated to the hand.
33
Protip: with problems like these, http://kobalab.net/majiang/dapai.html is a great help (it doesn’t do open
hands, but can be set to aka nashi). Often the expected value dierence between two good moves will be very small.
Try it on some of the examples in this chapter and see where it disagrees with the author!
34
bfor sanshoku is also not bad
1.5. IISHANTEN EFFICIENCY 107
Excellent oating tile (connect 4, nakabukure)×2
Example wertaadfjlnmm, cut l
Excellent oating tile + value-creating oating tile
Example qqyasdghjkzxnm drop zx for ittsuu/sanshoku
Example eriossfghhvbnm cut o for tanyao
Value-creating oating tile ×2
Example uoffghjkl33445 drop uo
Example qqweuolmmm,.44 cut m
Since creating a yaku enables us to call, this compensates for the loss in speed.
Extremely bad shape (overlap, less than 2 winning tiles) or conrmed worthless bad
shape hand
Example eeryoodhjjkbnm cut y
Example qeiossfghhvbnm cut o
Doesn’t give tanyao immediately, but a worthless (no yaku or dora with bad shape) 1-shanten
is not desirable anyway.
Example werioaaghhvbnm(2 u left) cut o
If 4 u are left, cut h.
Going from chiitoitsu 1-shanten to a wide or freely callable normal 2-shanten
Calling from chiitoitsu 1-shanten into toitoi 2-shanten, if chiitoi would have no yaku
or dora and toitoi would be conrmed mangan Especially with honitsu + yakuhai where
the hand would be expensive even with a sequence.
These are roughly the main cases, but in general we can decline a weak 1-shanten if we have
suciently good oating tiles. While we should be more prepared to stay in 2-shanten in the very
early game, if we have only 2 or 3 upgrades, we should take a weak 1-shanten even extremely early.
The reason is that we’ll have only 18 draws at best, and waiting for these upgrades will often take
much too long (11 turns on average for 3 kinds, 17 for 2 kinds).
108 CHAPTER 1. TILE EFFICIENCY
Easy to upgrade 2-shanten versus expensive 1-shanten
Even if the 2-shanten would be easy to upgrade, if the 1-shanten has a possibility of making a big
dick hand, the loss from returning is bigger. This is often a dicult problem. In the early game,
we’ll usually return, and preserve 1-shanten from the 7th turn on. We should also consider the
speed of the opponents.
Problem East 1, East seat, 7th turn, dora h
rrtsffghjvbnmh
Answer: m. While cutting s into 2-shanten has many upgrades, the loss from missing out on
dgk is very big. Rather than cutting t to keep the serial shape, we retain the possibility of
sanshoku, a perfect iishanten with sj and a sticky iishanten with ey.
This concludes the chapter on tile eciency. With the contents so far, we can usually choose
the right discard in an equal point situation when no opponents are attacking. From here, we’ll
take up other skills and some practice problems on tile eciency.
Chapter 2
Push-fold judgment
2.1 Dealing with non-tenpai opponents
Choking
So far, we’ve discussed ways to determine the best move without considering opponents. However, if
an opponent is in tenpai, we can’t just discard tiles we don’t need. If we want to defend rather than
attack, we should deal the tile least likely to be useful to opponents (folding). Deciding whether to
push or fold will be the subject of this chapter.
However, we can also say something about situations where no opponent is in tenpai, but we
still should be careful. One of these is choking (shibori). We mean purposely not discarding a tile
which we don’t actually need to prevent opponents from calling it.
When to choke
Cases where we should choke in the strict sense (merely to prevent opponents from calling, not to
not deal in or to use the tile ourselves) don’t really exist. That’s because we should discard tiles
that are useful to opponents early. The probability of dangerous tiles being called or getting
ronned increases continuously. It’s better to get rid of the tile early and increase our own chance
of winning.
Example East round, North seat, 6th turn, dora 1
erdf;hjvbn,,13 cut 1
This hand is mentanpin aka closed, so fairly sure of mangan. Even if we draw a second 1, we
still only get mangan. So we cut get rid of it early. If we didn’t have tanyao, we’d cut 3 instead,
since drawing a second 1 would double our score. If 1 weren’t dora, it’s useless and we should
get rid of it.
Even if a tile looks very likely to be called by an opponent going for a particular yaku, it’s often
not worth it to choke, since this will slow down only ourselves and one opponent, beneting the
other two opponents. We should only choke if we don’t care about helping the other two
opponents, most often in the following kind of cases:
109
110 CHAPTER 2. PUSH-FOLD JUDGMENT
An opponent has made a call for a clearly big dick hand (for example, choke yakuhai when
someone pons terminal dora)
With a big lead, we only need to prevent dealer or 2nd place from winning
If no one is in tenpai, it’s generally not necessary to care about opponents.
Dealing with getting choked
It can be good to refrain from calling if opponents would try to choke us in the following kind of
cases:
Calling would lower the score
We don’t have enough blocks
We intend to fold soon
We have an especially obvious yakuhai atozuke
Discarding good tiles rst
If we have multiple useless tiles, it can be good to discard the ones most dangerous towards oppo-
nents rst.
Early game
Example West seat, 1st turn, dora a
wtasshhm,22456 cut w
In this hand, we cut w over 4, but instead of keeping 4 as a safe tile because the hand is
bad, it’s more to create yaku (honitsu, chiitoi) more easily, making it a more useful tile. If we make
honitsu, we can keep it over the o suit tiles as a safe tile while staying ecient. With yaku that
restrict the usable tiles, keeping an honor over the disallowed tiles is common, allowing us to fold
easily against a riichi (we can often fold successfully if we have 3 safe tiles). However, if riichi is the
mainline, we should do everything to maximize win rate, so it’s not needed to keep safe tiles in the
early game.
1-shanten
Example West seat, mid game
wweuidfgjklzz4 cut 4
We should almost always prefer an eective tile over a safe tile.
Example West seat, mid game
wetydfgjklzzn4 cut 4
2.2. FOLDING TECHNIQUES 111
Even the upgrades into a wider are more valuable than a safe tile. In the late game, the two are
about equal.
1
When to keep safe tiles
We should discard tiles that are guaranteed safe but especially likely to become dangerous in the
future. For example, if an opponent is going for honitsu in souzu and n passes from a dierent
opponent, we should discard it even if it’s useful, especially since a ryanmen in souzu would be
dicult to win with.
If we’re still in 2-shanten or worse in the mid-late game, have low tile acceptance and can’t call,
our chance of winning is very low. Holding on to safe tiles with a hand like that is wise. However,
it’s better to hold on to several than to just one, and often it will be good to just fold completely.
The same is true about defending against damaten. If the hand is narrow and 2-shanten or
worse in the mid-late game, we should start being cautious about damaten.
Early game defense
In the early game when no one is in tenpai, it’s not really necessary to play defensively.
Even when leading in all last, the dealer can renchan indenitely and close any gap, so we should
try to end the match if we’re not the dealer.
Exception: player 50000, dealer opponent 25000, opponent 24000, opponent 1000. In this case,
even a big dick tsumo from the dealer won’t endanger us, so we can fold immediately to prevent
dealing in.
Exception: dealer opponent 55000, player 35000, opponent 8000, opponent 7000. Unless we can
realistically make a big dick hand, we can fold to avoid dealing in and secure 2nd.
If we’re dealer and have a big lead in all last, we only need to endure one more round. But
because dealer pays double on tsumo
2
, if an opponent could overturn us with mangan direct hit,
he could also haneman tsumo, and similarly for haneman direct hit and baiman tsumo. So instead
of going for a direct hit with dama, he could just riichi and tsumo, or instead of going for direct
hit with riichi, he could riichi tsumo ura/ippatsu.
That’s why even with a big lead, giving up on winning and stockpiling safe tiles is not a good
plan. Furthermore, depending on the point system, winning a hand can give a better point outcome
after the match. Of course, from the mid game on, if our hand looks hopeless we can fold against
dama, or fold against a riichi or call even from tenpai.
2.2 Folding techniques
Betaori
We’ll now discuss situations where an opponent is in tenpai. When we’re not in tenpai ourselves,
we usually should betaori. What this means is to give up on winning and discard tiles that are
least likely to be the opponent’s winning tiles. Since rounds where we won’t win outnumber rounds
where we’ll win greatly, learning betaori has a great impact on results.
1
This entire chapter is heavily based on Scientic Mahjong by Totsugeki Tōhoku and the author often gives no
explanation for why a move is good, referring to that book instead.
2
This is called oya-kaburi, “dealer hat”.
112 CHAPTER 2. PUSH-FOLD JUDGMENT
Danger level of tiles
Please memorize this diagram.
Diagram of tile danger level
rank type deal-in rate
S genbutsu 0%
A+ tanki honor 0.9%
A none
B suji 1 and 9 2.9%
C non-tanki honor 3.4%
D suji 2 and 8 4.8%
suji 3 and 7 5.5%
E no suji 1 and 9 6.3%
half suji 4, 5 and 6 7.0%
no suji 2 and 8 7.0%
no suji 3 and 7 7.1%
F no suji 4, 5 and 6 12.3%
Genbutsu are tiles discarded by the opponent or any tiles discarded after a riichi. Tanki honors
are those that can only be targeted by a single wait, so those of which 3 are visible. Double suji 4,
5 and 6 (r with both q and u safe) are comparable to suji 2 and 8, so rank D.
Factors that aect danger level
Kabe (no chance) is equally safe or safer than suji If all 4 e are visible, w can’t be
targeted with a kanchan, which it can if it’s suji. No chance tiles become safer the more of them
are visible (less chance of shanpon/tanki, this is also true for suji and honors). If all f are visible
and l is safe, h is also no-chance. Similarly if all f and k are visible. This is especially easy
to overlook.
One chance is safer than no suji but less safe than suji
Tiles outside of early discards are 1 rank safer About 60% as dangerous, even safer against
open hands. (Cutting e from wee early with an open hand is rare.) The earlier the discard,
the safer. The same thing is true of suji, so the suji of the riichi tile (ryankan suji trap) is slightly
more dangerous. Between a tile outside of an early discard and a suji of the riichi tile, we should
pick the former. (Note: since in kuitan nashi calls are less common, this technique becomes slightly
less reliable.)
Ura suji, aida yon ken No need to consider this.
Neighbors of the riichi tile (matagi suji) Sometimes more dangerous, but usually no need
to consider this.
2.2. FOLDING TECHNIQUES 113
Anko suji (The suji of a closed set in our own hand) Slightly more dangerous, but not by an
entire rank.
Dora and neighbors The dora itself is 1 or 2 ranks more dangerous (120–130% more dangerous
for tanyao tiles, 170% for terminals). Tiles next to the dora are about 1 rank more dangerous
(110%).
Suspicious discards (at least 3 dierent 456 tiles) Not a factor of itself.
A player who discarded an aka usually doesn’t have a regular 5 of the same suit (when
playing with 3) When ; has been discarded, dj are rank B (can only be targeted by penchan),
since from dd; cutting d is standard, and an aka tanki is preferable to a dj tanki. If ;
has been discarded and a is safe, f becomes much safer and similarly for ;, l and h. If an
opponent discarded /, the suji x, are safer than regular suji, since he usually won’t have a
ryankan suji trap (but aka traps do exist with some hands).
Discard order for equally safe tiles
When folding completely, consider the possibility of other opponents entering tenpai and keep
common safe tiles, discarding the rest rst. Conversely, when still considering our own
tenpai, we should fold with the tiles that are least useful to our own hand.
Among equally safe tiles, we usually want to discard the tile that opponents can call. This
is because opponents counterattacking into each other decreases the chance of having to pay for a
tsumo. However, if a draw looks likely and the open hand would be so expensive as to endanger
our position, it’s better to not let opponents call.
Eectiveness of wait reading
The theories of ura suji
3
and matagi suji have mostly been disproven.
Why ura suji is wrong
For example, the ura suji of w are e and y. The old theory is that from a wrt shape,
players would cut w early, so an early discard of w would make its ura suji more dangerous.
However, discarding a regular w also usually happens early, and we can’t distinguish between the
two. Furthermore, discarding w early makes e slightly safer by making a kanchan or penchan
less likely. In general, this kind of ura suji has a negligible impact.
However what about the ura suji of b, which are zvn.? This is because a b is a very
good tile, and discarding it early is rare. It only makes sense in a xcb or bm, shape, so an
3
裏スジ (n): frenulum of prepuce of penis
114 CHAPTER 2. PUSH-FOLD JUDGMENT
early b often indicates those shapes. While vn are already very dangerous anyway, if a b has
been discarded early, z. do become appreciably more dangerous. Similarly, a no suji , with
an early v discard also becomes more dangerous, but not enough to make it F rank. Since we’ll
rarely need to fold with tiles that dangerous anyway, this doesn’t really matter in practice.
Why matagi suji is wrong
The idea of matagi suji is that when the riichi tile is t, ey and ru become more dangerous
since the t will often come from a ryanmen pair. However, since a t is so strong, there are
an innumerable amount of other shapes where a player might want to keep it until tenpai. Also,
making no suji middle tiles more dangerous is rarely relevant.
However, if the riichi tile is k, hl do become more dangerous. This is because an isolated
k is rarely better than a middle tile, so shapes likes jkk and kll are especially common.
(This also is less than a 1 rank dierence.)
Principles of discard reading
Discard reading is the most useful when an opponent has discarded a very useful tile early, or a
usually not very useful tile late, since these allow us to infer the existence of particular shapes in his
hand. Similarly, an opponent who has discarded joints or pairs can usually be read to be holding
better ones. Conversely, an opponent who has only discarded honors before riichi gives us no hints
at all. Reading is only helpful when using the basic diagram from the previous subsection and
counting the number of remaining suji, and applying especially strong hints from discards to the
remaining tiles to pinpoint particularly dangerous tiles. However, when folding completely we’ll
often have many safe tiles, while with a strong hand it’s usually good to push even slightly more
dangerous than normal tiles. Discard reading is usually limited to situations where the decision
between attack and defense is hard, or when we want to defend but have no safe tiles.
Coping with having no safe tiles
What should we do if an opponent has entered tenpai and our hand is unfavorable for counter-
attacking, but we have no safe tiles? By this, we mean that all our tiles are rank E or F on the
diagram shown above.
For the time being, we should attack, and fold when we get more safe tiles. If we
have a bad shape iishanten with no safe tiles in the early game (because we didn’t keep safe tiles
to maximize speed), there will be many suji that have not yet passed, so risking one of them will
not be that dangerous.
However, if we have a 2-shanten or worse in the mid-late game and run out of safe tiles, our
chances of winning would be hopeless even with an all-out attack. In this case, it’s wiser to try to
minimize deal-in rate and deal-in score even by a little. The following techniques can be helpful:
2.3. DEALING WITH RIICHI 115
Cutting from a set or pair, or qr when u is safe, forcing through a dangerous
tile to create safe tiles for later Safer than cutting multiple dierent no suji tiles. Of course,
between multiple no suji tiles, we should prefer to cut the safest ones (terminals) rst.
Cutting tiles that would lower the deal-in score Especially terminals that would deny
tanyao, and avoiding tiles close to the dora. But because a riichi can have ippatsu and ura dora to
inate its value unpredictably, this method isn’t very reliable. It’s more useful against open hands.
Cutting tiles conjectured to be safe from discard reading Or rather, not cutting tiles
that look especially dangerous. We’ll explain this in more detail in the chapter on discard reading.
This technique is also more useful against open hands because a riichi will often have irime. (For
example, if an opponent declared riichi with a i, he often had a uii in hand, making a yo
more dangerous. But half of the time, he drew that wait rst and is now waiting on his other wait,
which would make yo irime, “entering piece”.)
2.3 Dealing with riichi
The average score of riichi
Whether to attack or to defend depends heavily on our own hand. We’ll rst consider the case
where we’re in tenpai, since otherwise we have to make estimate our chance of reaching tenpai,
complicating the calculations. From 2-shanten or worse, to fold is usually the right answer, but
from 1-shanten the decision will be especially hard.
Since with open hands, judging whether the opponent is in tenpai is not straightforward, but
we can infer a lot about his hand from discards and calls, we’ll consider the case where an opponent
has declared riichi rst and we’re also in tenpai.
It has been shown from statistical analyses of online play that with 3 aka dora in play, the
average score of a winning riichi is 7000 for non-dealer, 9800 for dealer. (Versus 6000 and
8400 with no aka.) While we’ll continue the rest of the chapter assuming the former, the dierence
is not very big and in aka nashi we should play only slightly more aggressively with the same value.
When in tenpai
Assumptions
Ippatsu, ura ari, 3 aka, shuugi
4
nashi.
If our hand is closed, we’ll declare oikake riichi. (This is almost always advantageous unless
our wait is on a safe tile. We’ll discuss examples of oikake dama later.)
We can safely avoid dealing in if we fold. We have enough (3 in the mid game, 2 in the late
game) safe tiles (B rank or up).
4
The retarded mahjong parlor rule where a set price (typically ¥1000) is added to the score for each aka dora
(often also for ippatsu, ura dora and rinshan)
116 CHAPTER 2. PUSH-FOLD JUDGMENT
The danger level of F rank tiles in the early game (4th turn), E rank tiles in the mid game
(7th turn), D rank tiles in the late game (12th turn) is roughly 5%.
The danger level of F rank tiles in the mid game and E rank tiles in the late game is roughly
10%. (The more safe tiles there are, the less safe the rest becomes.)
A lot of data is taken from Scientic Mahjong, so it’s for an average situation. If we have spe-
cial knowledge about the opponent’s style or the table situation, we can change our assessment
appropriately.
We don’t really care about no-ten payments our riichi sticks. If no-ten payments are impor-
tant, we should be slightly more aggressive in the late game.
We’re dealer
With a good shape
We should always attack. (Especially when considering renchan and no-ten payments.)
Only fold when we’re okay with losing our dealership and especially want to avoid dealing
in, or when we would have to push an extremely dangerous tile.
With a bad shape
In the late game (12th turn)
Cutting a tile with 10% danger level (E rank), with at least 3900 riichi.
Cutting a tile with 5% danger level (D rank), with at least 2900 open.
In the mid game (7th turn)
Cutting a tile with 10% danger level (F rank), with at least 3900 open.
Cutting a tile with 5% danger level (E rank), with anything but a 1 han hand.
In the early game (4th turn), we should push everything. (Discarding a 10% danger level
tile with a 1 han hand is slightly disadvantageous, but tiles are very rarely so dangerous
this early.)
Non-dealer versus non-dealer
With a good shape
In the late game (12th turn)
Cutting a tile with 10% danger level (E rank), with at least 2000 riichi or 2600 open
(riichi only and 2000 open are borderline).
Cutting a tile with 5% danger level (D rank), anything except 1 han open.
In the mid game (7th turn)
Cutting a tile with 10% danger level (F rank), with at least 2000 open (riichi only
is borderline).
Cutting a tile with 5% danger level (E rank), usually attack with anything (1 han
open is borderline).
2.3. DEALING WITH RIICHI 117
In the early game (4th turn), we should push everything.
With a bad shape
In the late game (12th turn)
Cutting a tile with 10% danger level (E rank), with at least 5200 riichi or 5200 open.
Cutting a tile with 5% danger level (D rank), with at least 3900 open (2600 riichi is
borderline).
In the mid game (7th turn)
Cutting a tile with 10% danger level (F rank), 3900 open is borderline.
Cutting a tile with 5% danger level (E rank), with at least 2600 riichi.
In the early game (4th turn), same as in the mid game. Attacking with a cheap hand
with no safe tiles and folding once we get some is an eective strategy.
Against the dealer
With a good shape
In the late game (12th turn)
Cutting a tile with 10% danger level (E rank), with at least 2600 riichi or 3900 open.
Cutting a tile with 5% danger level (D rank), with at least 2000 riichi or 2600 open
(2000 open is borderline).
In the mid game (7th turn)
Cutting a tile with 10% danger level (F rank), 2000 riichi is borderline.
Cutting a tile with 5% danger level (E rank), with at least 2000 open (riichi only is
borderline).
In the early game (4th turn), same as in the mid game, with the same caveat about
folding later being a good strategy.
With a bad shape
In the late game (12th turn)
Cutting a tile with 10% danger level (E rank), with at least mangan.
Cutting a tile with 5% danger level (D rank), 5200 riichi or open is borderline.
In the mid game (7th turn)
Cutting a tile with 10% danger level (F rank), 5200 riichi or open is borderline.
Cutting a tile with 5% danger level (E rank), with at least 5200, 3900 open or 2600
riichi is borderline.
In the early game (4th turn), same as above.
Recap
What we understand from this is that counterattacking is much better with a good shape,
and the requirements for a bad shape are quite strict, especially when facing the dealer. When
choosing which tile to call riichi with, we should also heavily emphasize a good wait. If calling riichi
with a head start, 5200 bad shape is better than 2000 good shape, but when chasing, the latter is
better: we should pick the good shape even if it halves value.
118 CHAPTER 2. PUSH-FOLD JUDGMENT
Choosing the wait against riichi
Cheap good wait or expensive bad wait
We should pick the the good shape even if it halves value. (Even riichi pinfu > riichi sanshoku,
since their average winning scores are about 3500 and 7100.) If the dierence is bigger than a factor
of 2, the bad wait is usually better.
Cut a dangerous tile into a good wait (or safe tile wait) or a safe tile into a bad wait
Unless a draw is close or we intend to go dama and fold immediately, we should cut the dangerous
tile to increase our win rate. This will lower our deal-in rate in the end.
Cut a dangerous tile for an expensive hand or a safe tile for a cheap hand
Unless the dangerous tile is especially dangerous, it’s a loss to cut a safe tile to halve our score.
Should we go dama if our wait is on a safe tile?
With a good shape, if we have at least mangan. Ryanmen dama 3900 or 5200 is riichi, 6400
or 7700 is dama. However, if we can’t expect going dama to increase our win rate (opponents aren’t
folding anyway or we are clearly pushing many dangerous tiles so they get wary and start defending
against us), we should riichi anyway. Of course, if our hand is too cheap to chase, we should fold.
With a bad shape, we should usually dama. But similarly, if we can’t expect a higher win
rate, we should riichi or fold. Since determining how much of a win rate increase we can expect
from going dama depends heavily on opponents, we’ll need to apply discard reading skills.
Dealing with 2 riichi
Good wait, cutting a common safe tile (in this subsection, we consider an honor shanpon
a bad wait, as we care more about tiles left in the wall than tricking opponents) On any turn,
win rate is about double deal-in rate, and ippatsu is common. Unless we especially want to avoid
dealing in, we should chase even with riichi only.
Bad wait, cutting a common safe tile Win rate is roughly similar to deal-in rate, so we should
attack if our hand has similar value to the opponents. If our hand is too cheap, we should take
dama and fold if we draw a safe tile (or call riichi if we can upgrade the wait or value). If we have
no other common safe tiles, we should chase. (But because a riichi duel usually ends quickly and
safe tiles are added more quickly too, we can usually fold successfully with only 2 safe tiles.)
Good wait, cutting a tile dangerous (10% danger level) against both Deal-in rate is
slightly higher than win rate, so we should attack only with a mangan. The same thing as above
holds about the number of safe tiles.
Bad wait, cutting a tile dangerous against both Deal-in rate is more than double win rate
(even more in the late game). We should only attack with a huge dick hand or when desperate for
points, and fold everything else. Even with no common safe tiles, we should try our best to not
deal in.
2.3. DEALING WITH RIICHI 119
Cutting a tile dangerous (10% danger level) against one Usually riichi with a ryanmen,
and fold with a bad wait that’s cheaper than 5200. Similarly for a tile that’s dangerous at the 5%
danger level against both opponents.
Folding against 2 riichi
We should of course prefer common safe tiles, but instead of cutting tiles that appear safe against
both (no suji terminals), we should cut tiles that are conrmed safe against one opponent.
We should emphasize not dealing into the opponent we don’t want to deal into (dealer or someone
who threatens our placement). While defending against 2 riichi is stressful, nding the safe tiles
against the more threatening opponent, and then choosing the tile that looks safest against the
other opponent makes it easy to defend.
What to do in borderline situations
We’ve listed some situations as clearly good to attack or defend, others as borderline. What factor
should we look to in these borderline situations?
Point standing and placement situation
How many safe tiles we have (folding success chance)
With 3 tiles in the mid game or 2 tiles, we can usually fold successfully. But what should we do if
we can’t?
0 safe tiles Can’t help but attack.
1 safe tile in the mid game We should also usually attack, unless we especially want to
avoid dealing in or would have to push an especially dangerous tile.
2 safe tiles in the mid game, 1 safe tile in the late game Attack in borderline situations
and fold otherwise.
Since it’s more dicult to defend with an open hand, we should be a bit readier to push with
open hands in sketchy situations.
Other players’ strategy
If other opponents are pushing dangerous tiles, we should fold more often. A ron between them is
more likely, and many safe tiles will be created allowing us to defend more easily.
When in iishanten
1-turn tenpai chance
A rough formula for the chance in in percent of reaching tenpai in 1 turn is
p = tile acceptance ×
5
6
120 CHAPTER 2. PUSH-FOLD JUDGMENT
Where 5/6 is an approximation of 100 divided by the amount of possible draws. While this
will depend in reality on discards and the tiles in opponents’ hands, it’s a good rule of thumb for
thinking quickly.
Tenpai chance 10%, guaranteed good shape
A hand like weooofgnnm,.j. (Strictly speaking, the tenpai chance is higher
than 10% if we can see less than 4 tiles of qrdh.) According to Scientic Mahjong, if we push
everything with this kind of hand, deal-in rate will exceed win rate, by up to double in the late
game. Even with an 18000 point hand, preserving iishanten isn’t worth it if we would have to push
a tile at danger level 7%. We should understand that tenpai and iishanten dier like heaven
and earth, and a double ryanmen iishanten is not particularly wide.
However, we should in fact attack with a hand like this in the mid game if we have non-dealer
conrmed haneman (12000) or better. The reason is that conrmed haneman is often either a big
dick chinitsu or a hand with many dora. Since chinitsu is easy to call which increases tenpai chance,
and having many dora means opponents will have less, it’s ne to attack.
20%
A hand like rtyuissdm,..., or a double ryanmen iishanten where we can call.
Win rate and deal-in rate are roughly similar, so we can push a danger level 7% tile with a mangan.
>20%
Common with headless or sticky shapes. Attacking with these while still not in tenpai can be quite
good, and we should treat them roughly as we do tenpai with a bad wait. This means all-out attack
with dora dora, and folding with no added value.
Callable hands
Since a tenpai is much better than an iishanten to counterattack with, we should call everything
possible if an opponent has declared riichi. (Unless we really need a big dick hand or we intend to
fold anyway if we don’t get a good draw.)
Example ertdffggkkvb4
While this hand is easily haneman closed, and we would try to complete it closed in an equal
scenario, if someone has already declared riichi, we should call into 1000 open tanyao.
<10%
Cases where it’s good to attack from a narrow iishanten (especially chiitoitsu iishanten) or 2-shanten
are extremely rare. The main exceptions are wide, expensive and easy to call 2-shanten (chinitsu
etc.) where dealing in would not change our placement.
2.4. DEALING WITH OPEN HANDS 121
2.4 Dealing with open hands
Characteristics of open hands
We’ll now discuss defending against open hands. Even against these, defending according to the
danger level diagram is eective. However, there are some unique points of judgment.
We don’t know if they’re in tenpai Except with 4 calls (hadaka tanki), we can’t be sure
unlike with riichi (in rulesets that disallow no-ten riichi :^). 3 calls in the early game (6th turn or
before), 2 calls in the mid game (around the 10th turn) and 1 call in the late game (13th turn or
later) are roughly 50% chance of tenpai. 3 calls in the mid game and late game are respectively
about 80% and 90%, 2 calls in the late game are about 70%.
5
Since cutting a tile of danger level 10% against an opponent who is 50% likely to be in tenpai
is the same as cutting a tile at danger level 5% against riichi, we should weight the relative values
of our and the opponent’s hand and decide accordingly. However, in practice estimating whether
an opponent is in tenpai will depend greatly on his discards, so we should exercise caution when
using general criteria like these. We’ll return to this subject in the chapter on reading.
The score is easier to read It’s hard to read how much a riichi is worth, and its value can get
inated by ura dora, so in the previous section we used a at estimate of 7000 (dealer 9800) points.
However, we can use reading skills to gauge an open hand’s value and decide to push or fold with
greater precision.
The wait is easier to read Often when a yaku like honitsu or toitoi is obvious, we can safely
exclude many tiles. Conversely, this makes tiles that can be targeted more dangerous than when
defending against a riichi, which can be easy to overlook. (There are many players who know how
to fold against riichi but have low awareness of open hands.)
The tiles after the opponent’s last tedashi are safe Even if an opponent has done tedashi,
6
,
tiles from several turns ago become quite safe against shanpon, and tiles cut by his kamicha from
several turns ago become quite safe against sequence waits too. It rarely happens that he was
unable to call to advance his hand and then drew the wait later. While it’s not needed to remember
all the tedashi and tsumogiri, it’s good to remember them for an opponent who has called. (Also
note that an opponent might decline ron to target us in particular, though this is very rare.)
The outside of early discards (especially neighbors) becomes safer than against riichi
Cutting w from wwe early is especially rare with an open hand.
The neighborhood of the tile that came out after the last call (sobaten) is dangerous
A perfect iishanten is common with open hands as it’s easiest to call into, and the tile that comes
out to make tenpai will often be from a paired joint to conrm the joint. However, calling from a
5
See https://blog.kobalab.net/entry/20180203/1517667551 for a table based on actual data
6
Tedashi refers to cutting tiles from the hand and keeping the draw, as opposed to tsumogiri, which is to
immediately discard the drawn tile.
122 CHAPTER 2. PUSH-FOLD JUDGMENT
paired joint and cutting the overow tile (eerchii wcut e) means another area is dangerous,
especially where no tiles have been discarded.
The area where no tiles have been discarded becomes more dangerous
Since shanpon waits are more common, the danger of live tiles
7
increases
Tenpai estimation
While the percentages for tenpai chance for a given turn and call count give a rough estimate, this
can change heavily depending on how many middle tiles an opponent has discarded. Since we can’r
get an exact chance, the decision to push or fold will depend to some degree on our own speed and
the opponent’s value. (But even against an opponent with 2 calls, we should fold with a narrow
2-shanten.)
If an opponent discards an especially useful tile (what this means depends on what yaku he’s
making, for example dora, suited tile in honitsu etc.), he’s likely to be in tenpai. If he cuts a very
useful tile, followed by a safe tile (dead honor), he’s especially likely to be in tenpai. In this case, a
ryanmen is likely, and the outside of the useful tile becomes a lot safer. (We can infer an extra tile
iishanten earlier.) This technique is of more limited use for yaku other than tanyao and yakuhai.
If other opponents are cutting dangerous tiles against a threatening open hand, they’re also
more likely to be in tenpai. If their hand is open too, they’re probably also in tenpai. Furthermore,
an opponent who declares kan is usually tenpai or 1-shanten.
8
Defending against specic yaku
Tanyao
Will be very common. Usually easy to read with an opponent cutting terminals and honors early
and holding on to middle tiles. When playing with aka, we should always be aware of how many
are still unaccounted for, since the opponent might be holding all of them. Dealing honors and
terminals is an easy defense against open tanyao, but sometimes we’ll get tricked by what was
actually yakuhai atozuke or concealed yakuhai. The following are often signs of a tanyao actually
being yakuhai:
Discarded terminals after middle tiles Might have been holding them as a safe tiles, but gets
less likely the more calls he has made and the more terminals discarded late.
Called a 23 or 78 ryanmen after having discarded the 5 earlier In real tanyao, it’s better
to discard 2 or 8 to avoid furiten.
To deal with this, if we’re going for yakuhai atozuke that could pass for tanyao and draw n
with m,. in hand, we should cut n. Rather than hope to draw /, it’s better to try to trick
opponents.
7
Westerners often misuse this to mean “dangerous tiles”, but it means tiles that have not been discarded by
anyone yet
8
This obviously depends heavily on meta and general skill level :^)
2.5. SUPPLEMENT 123
Yakuhai atozuke If an opponent has made any calls with terminals, this is the most likely reason
especially if other yaku are improbable. We should be aware of the number of live yakuhai left. It
can sometimes be good to choke live yakuhai (or fold if tenpai is likely), depending on how much
we care about the other 2 opponents advancing.
Sanshoku and ittsuu When 2 groups have been called, a wait for the 3rd one is likely.
Honitsu Should be fairly obvious to notice (o suit middle tiles and ryanmen in discards early,
yakuhai late). If he has discarded a suited tile or a live yakuhai, 1-shanten or tenpai is likely. If
not, tenpai is unlikely and we can often get of rid of suited tiles before it gets too late.
Toitoi Middle tiles of all 3 suits discarded early, possibly ryanmen dropping, yakuhai only late.
Live tiles become especially dangerous, while dead tile are safe.
Chanta 456 discarded early but no 3 or 7. 456 will pass.
Other yaku should not be that hard to defend against as they tend to be quite obvious. If we
can’t win realistically, we should fold from the mid game on against a decent open hand, cutting
tiles that invalidate yaku if have no safe tiles.
2.5 Supplement
Push-fold judgment just before a draw
Just before a draw, the chance of winning the hand is low, so score and a good wait become less
important and the danger level of the tile we would have to discard becomes more important.
We can estimate the danger level by counting the number of remaining suji and by other reading
techniques.
Assume there’s one opponent in tenpai, and pushing a tile would certainly let us receive no-ten
payments, while dealing in would cost a non-dealer mangan. Then we should push when the chance
of dealing in x satises
1500(1 x) 8000x > 1000
that is when
x <
5
19
= 0.263...
And similarly when x <
5
27
= 0.185... when pushing against a dealer mangan. This is unex-
pectedly high, but it assumes that we are certain of receiving no-ten payments, so if multiple turns
remain we should push only at a lower danger level. Furthermore, since the number of remaining
suji just before a draw will be low, we must bear in mind that even a single no suji tile against 2
tenpai opponents will be very dangerous.
This decision is heavily inuenced by point standing. Close to all last, it’s good to emphasize
expected placement over expected round value. For example, if we are last in South 3 and no-ten
payments would raise us to 3rd place, we can risk even a no suji tile, while if dealing in would drop
us by 2 or 3 places, we should usually fold.
124 CHAPTER 2. PUSH-FOLD JUDGMENT
Rolling
In mahjong, attacking maximally when we attack and defending maximally when we
defend is often the right answer. However, it can sometimes be valuable to attempt to preserve
the hand towards tenpai or a win while defending (especially in the late game for a formal tenpai)
if reasonably possible. We call this style of play rolling (mawashiuchi), or choking when dealing
with no-ten opponents.
When attacking maximally, tile eciency will tell us the best answer X, but sometimes cutting X
won’t be reasonable (yet) from a defensive standpoint. In that case, deciding which of the possible
less ecient moves to make is the skill of rolling.
When to roll
First, we should use the basic defensive criteria to decide whether it’s worth it to attack maximally.
If it isn’t, we can cut a safe tile that still advances the hand is some sub-optimal way if completing
the hand is possible. Often, when we have multiple isolated unsafe tiles against a riichi, it won’t be
possible to complete the hand anymore and we’ll have to fold. In practice, opportunities for rolling
will be few, and we’ll fold in the majority of cases.
How to roll
If we have to break up a group, the hand will almost always be fucked and we’ll have to fold, so we
should avoid that if at all possible. On the other hand, if we have a safe oating tile, we can cut
it without a problem: we won’t usually call that rolling, instead referring to the following kind of
plays:
Cut a tile from a complex joint Since this hurts speed the least, this is the most commonly
used. We use it when we have a tile that we don’t want to risk right now, but would be okay risking
once in tenpai. (If it would be too dangerous even in tenpai, we can’t use this method.) If we would
draw a pair or joint into the unsafe tile, we would drop a dierent component; if we would draw
another unsafe tile, we’d fold.
Dropping a pair or joint When dropping joints, we of course prefer to drop those of which
both tiles are safe. While this is more tile eciency, when deciding which joint or pair to drop in
a non-rolling situation, we should often keep the ones that opponents would be likely to call.
Dropping a set Slightly less bad than breaking a sequence since we get left with a usable pair.
Often amounts to folding.
Aiming for chiitoitsu Even with multiple unsafe tiles, we can always draw a lucky chiitoi. We
should therefore preserve this possibility, but often this will amount to folding.
Rolling is an extremely high skill cap low return skill that relies greatly on mastery of all other
mahjong skills. For a demonstration of rolling in practice, watch some pro games on Abema.
2.5. SUPPLEMENT 125
Ippatsu disruption and haitei shifting
We can also make unexpected calls with another purpose than winning and formal tenpai. We can
disrupt the ippatsu of an opponent who has called riichi or shift the haitei to a more favorable
player.
If we can call to disrupt ippatsu while advancing the hand, we usually should. Of course, if we
have a chance of winning which a call would negate, we shouldn’t call. If winning is hopeless, we
should call if we are condent in being able to successfully fold after (we have enough safe tiles).
In the late game, we should start being conscious of who will draw the haitei. It goes without
saying that we should only consider calling to shift it if we have enough safe tiles.
However, there are also cases where we should intentionally not make these calls even when
we could. For example, if we’re in a close placement duel with the dealer, so that an opponent
uninvolved in this duel would improve our placement by tsumoing a big dick hand.
Chapter 3
Reading
Principles of reading
Types of reading
In mahjong, there are several kinds of “reading”, but the most important ones (the ones with the
biggest inuence on results) are
Wall reading (how many tiles of a type are left in the wall)
Yaku reading (guessing which yaku an opponent is aiming for, as well as hand progress reading
and score reading)
Wait reading (how likely a certain tile is to be targeted by an opponent)
All of these depend on guessing what opponents hold in their hand from their discards (what
they don’t hold must be left in the wall). They can inuence both tile eciency (what tiles are
easy to draw) and push-fold judgment (how dangerous is this tile, how expensive does their hand
look).
Things to keep in mind
The foundation of reading is estimating the possible combinations of tiles And only
then the situation and the intentions of the opponents. For example, a sequence is much easier than
a concealed set, so at any given point, an opponent is much likelier to hold qwe than 555.
Furthermore, since there are always more unseen tiles outside of a particular opponent’s hand than
the 13 in it, it’s clearly less probable that a certain opponent has a pair of 5 than that none of
them have it.
Of course, if an opponent is going for honitsu or toitoi, or when 5 is dora, they become more
likely to hold it since they will keep it longer, so the probability of someone holding a pair or set of
5 will increase. However, since it’s statistically more likely to draw a joint or sequence, those will
be still be more likely.
127
128 CHAPTER 3. READING
It’s dicult to read rare cases (Instead of reading them, we’ll have to read what’s not the
case and deduce form there.) For example, it’s very dicult to specically pinpoint a riichi’s wait,
but reading what’s not the wait is trivial (genbutsu always pass). The probability of a particular
tile being the wait is much lower (usually 1/34 or 2/34) than it not being the wait (33/34 or 32/34).
There are some exceptions to this. For example, a player who needs to score 3500 in all last and
is in hadaka tanki with only a haku visible for score is obviously waiting on dora :^) Similarly, a
player who’s pushing all no suji tiles into a riichi is obviously in damaten for a big dick hand. But
being able to read rare cases with a high certainty is also rare.
We shouldn’t try to read where reading wouldn’t help Due to the nature of mahjong (high
amount of concealed information), situations where reading is eective to a high degree are rare.
Furthermore, often even being able to read won’t change our decision. For example, if we can read
a riichi’s hand accurately, but our hand is fucked, we’ll fold anyway. Often, reading incorrectly is
worse than not reading at all. In general, we should evaluate the situation from the certain
information, and fall back to uncertain information only when we aren’t sure.
3.1 Counting
The 1/18 rule
In mahjong, we’ll rarely be able to pinpoint waits exactly like Akagi Shigeru. In the majority of
cases, we’ll be able to exclude some possibilities, and work from there to get a probabilistic estimate
of the remaining possible options. The single most eective reading technique is counting the
number of remaining suji. When guessing an opponent’s wait, we’ll use this as the base. Since
there are 6 suji (14, 25, 36, 47, 58, 69) in each suit, there are 18 in total.
If there are 12 suji left against a good wait riichi, a no suji s will be targeted 1/12 of the time,
but a no suji b will be targeted 1/6 of the time (since 456 are each on 2 suji).
Of course, this is only a rough guideline. In practice, there will be other waits than ryanmen,
so we should treat these numbers as a high estimate. If pushing would be good even with a high
estimate, it’s denitely good to push. Conversely, since about 65% of riichi are ryanmen, the danger
level of no suji t can be estimated at 13/120 = 10.83% for ryanmen alone (low estimate).
If there are especially likely non-ryanmen waits (dora yakuhai, live yakuhai against honitsu,
especially suspicious suji traps), we can add them to the count. For example, if an opponent is
tenpai for manzu honitsu, and there are 2 safe suji and 3 unsafe honors, the danger level of no suji
w is 1/7 and of no suji t 2/7. We can understand from this example that when the amount of
possible waits is low, dangerous tiles become especially likely to deal in, which we should remember
when defending.
Honor waits
The following table gives a danger level of honors based on data of riichi between the 9th and 14th
turns:
Danger level of honors
3.2. DISCARD READING 129
yakuhai
cut held danger
0 1 7%
1 0 4%
0 2 4%
1 1 2%
2 <1%
cut held danger
0 1 5%
1 0 4%
0 2 3%
1 1 3%
2 <1%
guest wind
What can we learn from these data?
Against a late (9th turn) riichi, usually at least 5 or 6 suji will be safe. If there are 12 suji left,
the danger level of of 456 can be estimated as 1/12 = 8.3%. This is higher than the deal-in rate of
7% for live yakuhai. Therefore, live yakuhai are safer than no suji number tiles.
However, 7% is quite a lot, so we shouldn’t cut them from a hand that has a low chance of
winning. Even if it would destroy the hand, we should fold with another honor or a suji terminal.
Even the more because dealing in with a yakuhai tends to be more expensive than with a number
tile.
Honors that the opponents can see discarded are safer than those we hold in hand.
This is because calling pon on the rst one that comes out is common, and players tend prefer waits
they can see less of.
Furthermore, yakuhai are safer than guest winds at 1 held/1 discarded. This is because
of the aforementioned yakuhai pon, and because guest winds are classic choices for tanki.
3.2 Discard reading
Types of discard information
We’ll now start with the reading of particular discard patterns. The following kind of specic hints
are most often useful:
Calls Since these are part of the hand. Since we can see what specic tile was used to enter
tenpai with a call, we can read more precisely.
High value tiles cut early
Low value tiles cut late With value, we mean ease of making sequences (middle tiles are
high value) and tiles that help give a higher score (dora etc.)
Tedashi of joints and pairs We can understand that the opponent has more valuable joints.
The better the dropped joint, the more information we get this way. For example a riichi that
dropped a penchan can be almost any wait, but one that dropped a ryanmen is likely to wait
on a ryanmen or better. While dropping groups is rare, we can understand that the opponent
is going for an unusual hand.
Other rare cases We should always be on the lookout for sketchy things going on. For
example, an opponent who pushes dangerous tiles against riichi is probably in damaten,
especially if also in the lead.
130 CHAPTER 3. READING
Sobaten riichi
A long time ago, the theory that “the tiles around the riichi tile (last tedashi in the case of a
tsumogiri riichi) are especially dangerous” was widespread. This theory was disproved in Scientic
Mahjong.
The problem with this theory that the single riichi tile is not nearly enough information to be
able to deduce a particular pattern. We can think of many possible hands where the wait will be
elsewhere than around the riichi tile. To recapitulate from the section on iishanten theory, there
are four main types of iishanten:
1. Example qqqyussfghjcv
2. Example qqqyussfghccv
3. Example qqqyusdfghcvb
4. Example qqqyssfghjcvb
In all of the above, we are tenpai if we draw t. However, we’ll only discard a tile around the
eventual wait in example 2. Furthermore, even in this example, we won’t sobaten riichi if we draw
sxcbinstead of ti. (The probability of sobaten would be even lower of yu were yi.)
I hope we have made clear how low the success rate is of the sobaten riichi theory. In the majority
of cases, we can’t do any better than to count the number of remaining suji.
However, if we assume an iishanten of the appropriate type, we do get some information about
the wait. If we suppose that the probability of such an iishanten is 100% when an opponent has
called riichi with c, then the area around c will be targeted about 50% of the time. (The other
50% the wait in the area will have entered rst and the target will be the other wait.) Taking into
account all the possible shapes with a c like zzc, xcc, ccv, cbm etc. we can
arrive at a danger level for z of about 20%. This is considerably than the roughly 8.3% we’d
expect from counting suji, so the theory can be said to be eective. If the opponent has called and
then discarded c, the probability of sobaten will be double, since we know the other area entered
rst. So how often will an opponent have this kind of iishanten? We’ll talk about that next.
Gyakugiri
One of the cases where a perfect iishanten is likely is when a high value tile has been cut early
and a low value one late.
With an extra tile iishanten, it’s normal to cut a high value tile that’s useful for upgrading the
wait late. (the exception are hands with 2 ryanmen that want to keep a safe tile.) The same is true
for sticky iishanten. If the probability of these shapes is low, a perfect shape is more likely, with
for example a late q discard likely to be from qqw qqe qet etc.
3.2. DISCARD READING 131
For example, let us consider the opponent who called riichi after discarding gs. If it wasn’t
a perfect shape, what could it have been? In an extra tile or sticky shape, it makes no sense to
keep s over g unless going for sanshoku or chanta, or holding sdd hoping to upgrade into
a wider headless iishanten with af. We can hardly imagine an extra tile iishanten where both
sg were useless, since he would have discarded s very early. In a headless shape, we can
imagine sssg, cutting gs to make s the head, or asg/sdg cutting g rst
and drawing a/d to make the head (rare). It is also possible that he cut g before another
opponent called riichi, stopped on s for a bit, then rolled into tenpai and risked s.
What should be observed here is that all of the above are rare cases, and the simple case of a
perfect iishanten will be more likely unless we have extra clues.
We can easily imagine this discard order from aasg or ssdg (very rarely from
sddg when aiming for tsumo sanankou), so that f and especially paia will be more danger-
ous.
The deal-in rate of a will be
(1 rare cases) × (1 irime)
Since the probability of irime is about 50%, the deal-in rate of a will be about 40% assuming
20% chance of one of the above rare cases. Since ssdg will be more common than aasg
(it’s common to cut srst from aasgbefore iishanten), the deal-in rate of fwill be roughly
25%. While this is a back-of-the-envelope calculation, pushing a tile at that danger level only makes
sense with a good wait mangan tenpai.
If an opponent discarded g and then called elsewhere and discarded s, we can eliminate irime
and the danger level of a will be even higher.
This kind of gs anti-ecient discard order is called gyakugiri. With gyakugiri, the area
around the second tile becomes much more dangerous. With other patterns, we’ll be able to adapt
the above idea, but there will be more exceptions, so we should remember that 52 and 58 gyakugiri
reading is the most eective.
Patterns of gyakugiri
gs with other tedashi before declaring riichi The probability that the area around s
has been completed becomes higher. If we think that the probability of the wait being in that area
when s was cut at tenpai is 1/2, we can think that it’s 1/3 (3 incomplete joints left to complete)
when s was cut at iishanten. However, we can’t exclude other iishanten types. As the number of
tedashi afterwards increases, the probability decreases further. Therefore, we can’t really consider
this kind of reading more eective than counting suji.
132 CHAPTER 3. READING
t (middle tile from other suit)s We can add the cases of tsdfgsticky iishanten,
ittsuu, honitsu which won’t make a big dierence, but instead of just aas and ssd we
can imagine shapes like ssf, sff, sfh and rarely sfghhj. The danger level
of a will thus be about 30–50% that of the gs case (15% in total, about F rank), which is
still more dangerous than the 8.3% we would expect from counting suji. f will also be a bit more
dangerous, but not especially more than the 16.6% we’d estimate from counting.
hs Instead of just aas and ssd we can imagine shapes like assh (suji trap)
and ssfh. The rest is similar to gs. awill have a danger level of about 20%, f won’t
be especially dangerous.
hrightarrowd When playing with aka, cases with sticky iishanten will be unlikely, but we can’t
be as sure as with gs. Also, it’s not just af but also sg that become more dangerous.
Since fg will generally be ryanmen, and s will also usually be targeted with ryanmen (cutting
a from add for a suji trap), it’s only a that becomes especially more dangerous.
(middle tile from other suit)d We can think of numerous exceptions, so reading is not
very eective. a will be slightly more dangerous.
Summary
With gs riichi, a is especially dangerous, f is more dangerous than F rank.
With hs riichi, a is about F rank or a bit worse.
With middle tile of another suit s riichi, a is more dangerous than normal but not F
rank.
With d riichi, a is more dangerous than normal.
Call reading
We’ve discussed before how a perfect iishanten with paired joints is more ecient with an open
hand. However, we can’t exclude other types. Here, we’ll discuss some examples where we can infer
that an opponent has a perfect shape.
3.2. DISCARD READING 133
This is a tonpuusen sudden death overtime with 30000 to win. Blue lines indicate tsumogiri,
the tiny illegible insets are (from top to bottom) 7m chii, haku pon, hatsu pon. Source is a dead
mahjong BBS post from 2008.
1
While we want to cut b into tenpai, toimen’s call is worrying. What should we do?
Calling chii on u and cutting v certainly makes the area around v dangerous. However, we
can’t be sure he had a perfect iishanten. Since winning this hand will put us in 1st, we should risk
it and push b. However, this hand is indeed a perfect iishanten, since he cut t from tpy,
and it would make no sense to keep a v if it was being used as just a oating tile. So he must have
had something like xxv, cvv and vvb (accounting for the fact that he cut m and
2 c are visible). Here, we can eliminate vvb since he would have called chii on the dealer’s
discards. So the remaining possibilities are xb ryanmen and x + something shanpon. Since
cutting b has an extremely high chance of dealing in and dropping us to 3rd place, we should cut
n preserving tenpai defensively.
Summary: opponents who cut from a paired joint are likely to have a perfect shape
(other paired joints)
1
10hoe looks better nowadays :^)
134 CHAPTER 3. READING
Dora discarding
Dora discarding riichi
Unless the hand is suciently expensive (chiitoi with 2 more dora, menhon chiitoi etc., all very
rare) a tanki wait is very unlikely. Furthermore, the chance of a ryankan suji trap becomes
lower unless the hand is already expensive enough. However, we don’t really know anything else.
The reason is that a dora is so valuable, almost all closed hands naturally want to keep it until very
late if possible, even isolated. Since the information value of keeping a dora until late is low, we
can’t use it to deduce a certain shape.
While “suji that cross the dora are safe against dora discarding riichi” is a proverb, this is not
actually reliable enough to make these suji safer than other untried suji.
Dora something else riichi
Conversely, in this case we have more information to work with. It’s easy to understand that
a dora-related wait becomes less likely. Exceptions are hands like werdffxxvnn
dora f or weeyui;hhxcv,, dora h keeping the dora worsens the shape and
makes it harder to make yaku. We can’t really read these, but they’re rare cases. This technique
becomes more powerful with a more central dora. For example, i dora discarded makes yo
ryanmen, uo shanpon, u penchan as well as tu kanchan safe, while g dora makes all pinzu
waits except penchan, askl shanpon and afhl ryanmen fairly safe.
Furthermore, we can read that a perfect iishanten is common from the following reasoning:
Dora is the strongest oating tile, so an extra tile iishanten is unlikely.
Same for sticky iishanten. While an edge dora is hard to stick to, discarding a middle tile
dora is especially rare.
Headless iishanten is also slightly less likely. For example, in qqwedora q, we’d rather
conrm a dora pair than cut q into headless iishanten.
However, other types can’t be eliminated. Furthermore, if combined with gyakugiri to make
dora gs, we can be almost 100% sure of a wait around s. The only notable exception is
headless sssg.
Example 3k5.p;
i
c dora u
If the area around i isn’t irime, we can read that the wait is either yo or o + something
shanpon. So the danger level of o is about 50% and y about 25%. We should only consider
cutting o with a good wait mangan tenpai. (Similarly for dora hd.)
(If you’re curious, the hand in the actual game was qweuioozxcjkl.)
3.2. DISCARD READING 135
Joint dropping
What we can read from joint dropping
An opponent who drops a joint is holding on to a better (rarely equally good) joint
unless he’s folding
If an opponent enters tenpai immediately after dropping a joint, he doesn’t have
a headless or sticky iishanten (The exception is dropping ew from wwwe or a sticky
shape going from tenpai into a better tenpai.)
Before reading any more, we should remember the above points. If an opponent drops a joint
before iishanten, he might also be holding a oating tile instead of a better joint. Of course, the
better the dropped joint, the more we can infer.
Types of joint dropping
Penchan The weakest joint, so gives the least information. The hand is more likely to be close
to tenpai when dropping from the inside out (wq) than from the outside in.
Kanchan Doesn’t have a penchan unless it gives dora or yaku. When cutting eq, he doesn’t
need an upgrade to ryanmen with r, so either has a qety shape or all ryanmen left. We
can usually expect a ryanmen end shape (or a headless shape tanki). When cutting from the inside
out, a wt wait is hard to imagine so w will usually pass (and t too if i is safe). While there
are exceptions related to dora and yaku, there will be less traps than with suji, so the tile that
completes an outer kanchan dropped from the inside out is safe.
Ryanmen We can expect a ryanmen end wait (or headless shape tanki). If we know for sure an
opponent has a ryanmen, suji and honors are safe. Therefore, the danger level of no suji tiles
becomes equal to 1/(number of remaining suji).
While this isn’t pair dropping, an opponent who declared riichi with a safe tile will also usually
have a ryanmen (especially in the early game), since with a bad shape it’s often good to keep a
oating tile for upgrading the wait.
Exceptions
While we say that an opponent who drops a kanchan from the inside out usually has a ryanmen or
a dora/yaku-related bad wait, there are exceptions. With rw, a shape like qqwr into q
+ something shanpon is possible. Especially with r something else w, a simple kanchan is
hard to imagine. q is suji, but if a rw kanchan has been dropped this way it’s as dangerous as
no suji, since it’s hard to draw into qqw and irime will be rare. Conversely, with wr, q
will usually be safe.
When choosing which ryanmen to drop, there are some that are preferable, for example overlap-
ping shapes like ssdd and sdgh. If an opponent has dropped sd, we can be liable
136 CHAPTER 3. READING
to think that af are safe, but this is not true. Especially with some other discards in between
s and d, af become very dangerous.
To summarize, if an opponent drops a joint with some time in between its two tiles, he’s usually
holding on to another shape in the area of the second tile (else he would prefer another oating
that doesn’t create furiten).
Tedashi ryanmen something else riichi
We can infer that the opponent dropped the ryanmen with too many joints before iishanten. There-
fore, the tile that came out after must probably have been connected to another ryanmen somehow.
Suppose that it was u, then yuu and uui are the most likely candidates, making ti
and yo dangerous. While a shape like rrttyu into ey wait is also possible, this is of
course much less likely. With a dropped kanchan, sobaten also becomes a bit more likely in this way,
but there will be many more exceptions (oating tile for upgrades etc.). With penchan dropping,
it’s normal to keep a normal middle tile, so we can’t really deduce anything. If the dropped joint
contained or accepted dora, we can be especially sure of the read.
Dropping a dora bad shape joint
We can infer than the opponent has a better joint, so either a yaku-creating bad shape or most likely
a ryanmen. When cutting /c, a shape like xcc/is common, so zvare dangerous. The
other possibility is a big dick hand that cuts / rst for safety. When cutting c/, xcc/
into zv wait is also suspect.
Dropping a dora ryanmen
When dropping a dora-accepting ryanmen, the most common reason is an overlapping ryanmen,
with a dora-containing ryanmen a double overlapping ryanmen. The exception to both are big dick
single suit hands. When cutting f; in 3 aka rules, a shape like ffg; can be eliminated
(though there are some players who will do this with a conrmed mangan to trick opponents).
Outside of an irregular hand, we can think of a headless iishanten that entered ; dama tanki and
then declared riichi after changing the wait. If the dora was discarded rst, we should be especially
wary as a big dick irregular hand is likely.
Pair dropping
What we can read from pair dropping
A tanki wait is unlikely
A headless or sticky shape is unlikely
The opponent is holding a better (or rarely equally good) pair
3.2. DISCARD READING 137
Pair dropping with an interval between the two tiles
With an honor pair, we can think of keeping the second tile as a safe tile (so ryanmen extra
tile iishanten is likely), but with a number pair, the second tile most have had some purpose.
While ukase-uchi is possible, situations where it’s ecient are rare, so we can assume the tile
was connected to another pair or joint. For example when dropping e something else e,
shapes like qqee, eett, eetu, eetyuui are possible, while shapes
like eeer or weee will be uncommon, so qr and wt will be hard to target and
especially w will be safe.
Honor pair A ryanmen wait is likely. The reason is that with a bad shape joint, it’s common
to prefer the honor pair aiming for honor shanpon. When dropping a yakuhai pair, pinfu is likely.
Dropping a double yakuhai (renfonpai) pair is a surere sign of a big dick pinfu (menpintan dora
or worse) so we should be very careful.
Aka containing pair Either a big dick hand with yaku or likely to have an omote dora pair
with ryanmen wait or better. It’s common to prefer an aka pair over a bad shape joint, so a
ryanmen is likely. We should also be careful.
Dora pair Either a honitsu, chinitsu, yakuman or chiitoi with the other 2 dora. Needless to stay
we should be extremely careful.
This kind of yaku reading becomes more eective in open hands. If an open who’s going for
toitoi drops a pair, he has a better (easier to call or yakuhai) pair. If a calling opponent drops
a yakuhai pair, he’s usually going from yakuhai atozuke into open tanyao or from honitsu into
chinitsu. An opponent who drops a renfonpai pair has a big dick hand. Unless it’s the late game
and he wants to make even a cheap tenpai, tanyao dora 3 or chinitsu is likely. If a clearly expensive
call has been made and we’re far from tenpai, we should usually fold.
Yaku reading
So far, we’ve focused on reading the wait of a riichi under the assumption that opponents will play
eciently to maximize speed. In this case, aiming for yaku is more of an exception. We’ve already
given a short overview of how to tell which yaku an opponent is going for in the previous chapter
as it’s not that dicult.
We can use discard reading on opponents that appear to be going for even very rare yaku. For
example, suppose an opponent has called pon on 1 and 2, and then dropped a pair of 6, then
we can be quite sure he’s going for shousuushii.
However, reading the yaku of a riichi is a problem. We can read common yaku like pinfu and
tanyao being likely when the opponent drops an honor pair, but reading sanshoku or ittsuu is almost
impossible. We can at best read that an opponent who has dropped a ryanmen usually won’t be
going for a sanshoku or ittsuu bad wait.
If an opponent has many middle tiles in his discards, the probability of an irregular hand does
increase, but we can’t eliminate that his haipai could have been very good (which is quite common).
To read an irregular hand, we need evidence that the opponent did not advance straightforwardly.
138 CHAPTER 3. READING
Example South 1, dora s (source: Sasaki-pro’s hand in an online tourney)
.hnm
3
(all tedashi)
The point here is that he dropped nm to keep 3. If 3 were a number tile, we’d expect
sobaten around it, but we can only imagine a regular hand advance with cutting 3 from an anko
headless shape. Since we can assume it was used to make yaku, we can narrow it down to manzu
honitsu and chiitoitsu. In this particular game, the dealer, Fujisaki-pro, risked a u with a chiitoi
dora tanki and dealt into a haneman (riichi honitsu double south). While with a dealer chiitoi dora
dora, it might be worth it to risk it, with a cheap hand it should be no problem to fold even from
good wait tenpai.
We’ll now discuss some examples of how “sketchy calls” can be used to read yaku.
Example dora 7, 4 is a guest wind (source: Dahime Obakamiiko, Umasugi’s hand)
sdfghjkl445577
Here, Umasugi cut 5, called pon on 4 and cut 5. This is quite a sketchy call from the
opponents’ point of view. Since 7 is dora, they can read that she has at least two 7 and
discarded 5 because 4is easier to call and she doesn’t need any more points. While an exception
would be going for shousuushii, this is of course extremely rare. Since a 7 pair requires another 2
han for mangan, we can narrow the possible yaku down to honitsu, toitoi and chanta sanshoku.
The idea behind this play was that if afj enter rst, 4 will come out easily with the 5
pair in the discards. However, cutting 4 and calling pon on 5 can also be a haku only, or no-ten
(cutting a guest wind pair from a weak hand is common). On the other hand, the sketchy 4 pon
after dropping the pair of 5 is likely tenpai. If there isn’t a dierence in score, plays like this
that aim to trick to opponent are good (afj for the trap are more likely to come rst than 4
that’s easy to read), but here I think that the straightforward 4 dropping is better since there’s a
chance at haneman or baiman.
Tanyao with 2 calls that called
v
xc chii and cut m
The mainline is kuinobashi from xcvbm into a cn wait. Going for tanyao with a xc
uncertain shape, it’s rare to make 2 calls to other parts of the hand. However, even if this play
makes the wait obvious, it’s still eective to extend the wait hoping for tsumo.
l pon, then
z
xc chii and cut v next turn
We can read chanta, but with another yaku (otherwise, wouldn’t call uncertain lpon), usually
yakuhai or sanshoku doukou. (very rare in actual play)
3.2. DISCARD READING 139
Sobaten tanki
Sobaten can also occur in a headless shape. For example, drawing or calling chii on ru into
tygh will create a sobaten tanki. While this is very dicult to read in closed hands, and
not calling riichi while waiting for the wait to improve will be common, it’s especially easy to read
in hadaka tanki (almost certainly sobaten tanki) or other open hands with many calls. Of course,
when a tedashi is made after the call, the theory no longer works. Furthermore, we can often discern
a tanki wait by the opponent doing multiple tedashi after calling into what appears to be tenpai.
Chiitoitsu reading
Apparently, Totsugeki Tōhoku (whose real name turns out to be 作田, Sakuta Makoto) wrote an
article about imperfect information games and presented it at a symposium. Notably, it included a
simple program that was able to detect honor waits and chiitoitsu with higher accuracy than any
of a sample of 30 human mahjong players.
The algorithm for detecting honor waits was based in several criteria, such as
A certain number of middle tiles discarded before 3 honors and terminals
At least 40% of the discards are middle tiles
At least one live honor exists
A certain number of live or once discarded honors exists etc.
2
The algorithm for detecting chiitoi was based on a single criterion.
The riichi tile is a live or once discarded honor
With simple criteria like these, a computer was able to surpass human players’ “reading skills”.
Takeaways
The foundation of detecting honor waits is counting few suji left and many honors left. The
most important factor in detecting chiitoi is that the riichi tile is a good tanki tile. We
can combine these techniques with those discussed before for reading irregular hands, for example
ryanmen dropping in discards like yu
3
Eective wait reading situations
We’ve discussed the main cases where reading a specic shape is more signicantly more eective
than counting alone. However, making a specic read successfully often won’t change our strategy
(for example, if we’re already folding).
Suppose there are 11 unsafe suji left, and we have read one of them to have a danger level of
50%, then the remaining 10 each have a danger level of 5%. When in tenpai, we’d stop only at the
2
Can’t nd a full description of the algorithm sadly
140 CHAPTER 3. READING
extremely dangerous suji and push the rest, but with a weak 1- or 2-shanten it’s not worth pushing
any unsafe tile.
Conversely, if we want to fold but have no safe tiles, we should prefer to cut even slightly safer
tiles, such as suji when we are highly certain of a ryanmen riichi, or the area around the dora if it
has been discarded.
Cases where we can eectively read an irregular hand are rare. Even AI can only read honor
waits correctly about 30% of the time. However, if we assume there are at least 2 honors left, then
the danger level of each one would be 15%, which is not much higher than a no suji number tile. We
will almost never risk a no suji number tile over an honor, and we will usually simply fold anyway
(same for chiitoi, defending as against a regular hand).
Hand progress reading
An opponent can be read to have a fast hand if he discards many middle tiles early without holding
on to terminals and honors. Similarly, an opponent going for a certain yaku is usually close to
tenpai if he discards tiles related to it.
However, these are vague and not very eective techniques, since in mahjong, knowing how far
an opponent is from tenpai is much less important then knowing whether he’s in tenpai at all. It
can maybe play a small role in deciding which opponent to keep safe tiles against (keeping the
dealer’s or the placement rival’s if no specic information is available).
Another obvious but important point to be made is that an opponent who is folding is never
in tenpai, and we can ignore defending against him. We can usually detect that an oppponent is
folding if he tedashis several safe tiles in a row, or breaks up a safe tile pair or concealed set.
3.3 Wall reading
Advantages of wall reading
We can decide more easily when unsure about which joint to drop
We can keep easy to draw tiles when going for chiitoi
We can know which wait is easier to tsumo
We can estimate what tiles opponents are holding
We can make more precise push-fold judgments (folding in borderline situations if few tiles
are left in the wall)
What we need to pin down rst is that no matter how well we read the wall, it’s still
uncertain information. If without reading the wall a certain move is clearly more ecient or gives
better value, we should play it without hesitation. Choosing a kanchan over a ryanmen because
it’s certainly live in the wall is nonsense.
We should only use wall reading in situations where we have diculty deciding based on certain
information, the “borderline” or “dicult” hands discussed before.
We should also note that wall reading does not have a major inuence on results, and it’s wise
to make decision based on reading the opponents’ hands over wall reading.
3.3. WALL READING 141
Tile group reading
To read the wall, we need to know what tiles opponents are using to build their hands. Same as
with wait reading, we need to read “combinations of tiles”.
Please remember the following points
We can get a rough idea of how easy it is to make a sequence with a certain tile
We usually can’t read if an opponent is holding a pair or set of a certain tile, so
we don’t try to
Tiles that are dicult to make sequences with but aren’t discarded are more likely to be in
the wall. This applies to honors as well as tiles outside of kabe (4 tiles discarded) or tiles outside
of heavily discarded tiles. For example, if 3 u, 3 i and only 1 o have been discarded, the
remaining o are likely to be left in the wall.
If an opponent is clearly going for a honitsu or toitoi, we’re liable to think they might hold a
pair of the yakuhai we have a pair of. While with obvious yakuhai atozuke this is logical, with
honitsu and toitoi it’s still much more likely that our nal 2 yakuhai tiles are left in the wall than
that the opponent has both of them.
Suit reading
We’ll now investigate the concepts of “expensive suit” (discarded little, harder to draw) and “cheap
suit” (discarded heavily, easier to draw).
Seeing which suits are expensive or cheap is easy from just looking at the discards. Since the
opponents are more likely to hold tiles of the expensive, it’s less likely to be left in the wall and vice
versa. Since opponents will make less sequences with it, the cheap suit is not just easier to draw,
but also easier to win on and to call.
Example rrtffgkkxcvm,. cut r if manzu is cheaper and
fif pinzu is cheaper, xing the stronger (easier to draw) joint.
We wrote earlier that a ryanmen wait that opponents might hold is better than a kanchan that’s
certainly in the wall, but how about a 5-tile wait that’s certainly in the wall? Please consult this
table (source: https://blog.goo.ne.jp/21_/e/3676af9ce718a9d97f07100ba5dd0356)
Probability of drawing a tile
n opponents might hold certainly in wall
1 14% 21%
2 26% 38%
3 37% 52%
4 46% 63%
5 54% 71%
6 61% 78%
7 66% 83%
8 71% 87%
142 CHAPTER 3. READING
Bearing in mind that we will rarely be able to know tiles are left in the wall with 100% certainty,
we can see that it’s rarely good to choose a narrower wait based on wall reading.
However, with a very wide hand, dierences in tile acceptance matter less, so we can more easily
change our decision based on wall reading.
Example yudfghjcccvbbb
We’d usually cut c or b, but if manzu is expensive we can drop yu.
Reex reading
We can also read the wall from an opponent’s discards more specically. However, this method is
not very eective. While an opponent who cut q is slightly less likely to hold w, we can think
of numerous exceptions, to say nothing of the other two opponents. However, if we have no other
factors to decide with at all, we can use the following two rules:
An opponent is less likely to hold the neighbors of a tile he discarded
An opponent is more likely to hold the suji of a tile he discarded
Example When choosing which kanchan to break from qeuo, we should keep qe if
many qe have been discarded by opponents.
Example When choosing the end wait from dgj, we shouldn’t choose f if many aj
have been discarded. The ease of creating a suji trap after riichi also plays a role here.
With honors, from the mid game on, honors discarded once are more likely to be
left in the wall than live ones, since opponents did not call pon on them. While if we want
to stack yakuhai, we should prefer live ones (since we want a whole set), we should prefer once
discarded honors when going for chiitoi.
While the dierence is very small, if kamicha just discarded 57, 5 is more likely to be left
in the wall, since shimocha and toimen have not yet had the opportunity to match 7 now that
it’s not live anymore.
3.4 Supplement
Disguise
Since opponents will try to read our discards, it can be good to prevent showing them important
information.
For example, we should cut w from wert so that opponents won’t know ti are safe.
Since tedashi gives out more information than tsumogiri, we usually shouldn’t karagiri (tedashi an
identical tile to the one just drawn).
There are some exceptions where it’s advantageous to give opponents more information. For
example, if we cut gfrom fggand immediately draw another g, we should karagiri to create
3.4. SUPPLEMENT 143
the illusion of dropping a pair, making a dh appear unlikely. When in damaten for a riichi’s safe
tile, we should karagiri safe tiles to make opponents think we’re folding.
Even if our hand is very bad, we can make threatening discards to make opponents wary.
It’s sometimes even good to give opponents true information instead of false. For example, as
non-dealer in all last we can try to make our wait more obvious with karagiri and hope that 1st
place will deal into us on purpose to end the match.
However, techniques like these are not very important, and we should remember to have things
closer to the core of mahjong have a bigger inuence on our play.
Gyakugiri II
An appendix to the subsection on gyakugiri.
We’ve discussed the main patterns of gyakugiri, but the same can be applied to any high value
tile low value tile discards. For example to makes the suji i quite dangerous, and cutting
j late with all 4 h visible makes kl suspect. If the tile discarded into tenpai wasn’t a safe
tile, and there was no irime, then it must have been sobaten.
Another point which we should bear in mind is that late terminal discards can be signs of
upgrades or slides, for example cutting . when drawing n with m,., m. or ,.. While
we can’t conclude the wait is likely to be around that area, we can be fairly certain a sequence
exists there.
(red lines are tsumogiri)
144 CHAPTER 3. READING
Here, the late l tedashi is suspicious. Drawing h into jl is mainline, but even if that’s
not the case the opponent is likely to hold at least one j. Since that means there are only two j
left, we should fold.
Lag reading
Not as important as other kinds of reading, but still worthwhile to remember.
Lag refers to the small pause that is inserted after a tile is discarded in online clients while
players consider whether to call. While many clients sometimes add random lag to discourage lag
reading, it’s nevertheless possibly to notice the dierence with some practice. Since lag reveals
information to opponents, we should usually play with calling o if we don’t want to call.
However, we should be careful since there are many non-obvious calls like kuinobashi that are still
good to make.
While we don’t know whether the lag on a certain tile is for chii, pon or kan, it’s clear that if
it’s for pon or kan we get more information. There are many possible patterns where it’s possible
to call chii, but if it’s possible to call pon, one of the other 2 opponents must have at least a pair
of the tile. We can be sure lag is for pon if
the tile is an honor
it was discarded by kamicha
it’s obvious that the discarder’s shimocha can’t call it (in riichi or clearly not holding the
required tiles)
we’re playing sanma :^)
If there’s pon lag on a tile that we also hold, we can’t draw a second one, so we should discard
it immediately if we originally wanted to stack it. Similarly, if there’s pon lag for a tile which he
have a bad shape joint waiting on, we should break it as there’s only 1 tile at most left in the wall.
If an opponent calls riichi with a tile that was previously pon-lagged, sobaten from a perfect
iishanten is likely.
Tiles outside of a pon-lagged tile becomes a bit safer, as one-chance tiles. If we can see one more
tile, they’re no chance and comparatively safe.
Tile arrangement reading
Since players will usually arrange their hand sequentially, it’s possible to read it based on this
arrangement. While there are players who don’t arrange their at all, this makes it much easier to
make tile eciency mistakes and thus isn’t recommended.
We should pay attention to not make our hand too easy to read. By applying the following
rules, we’ll be ne
Sort by suit, with the order of the suits and honors random.
Sort each suit in order, but sometimes in reverse lke ewq
3.4. SUPPLEMENT 145
Don’t put tiles that we want to call or discard at the edge
For example, if we put 55677 at the right edge, call pon on 5 and discard 6, it’s
easy to read that we have a pair of 7. We should put these tiles in the center of the hand
instead and completed groups at the edge, possibly reversed. However, if we might want to
call into our completed groups, for example pon a or s into aassd, we should put
these groups in the center and out of order, like aadss
We should arrange joints we want to call so that there are no tiles in between. For example,
with zccvb tenpai waiting on x, we want to extend by calling chii on v. However,
exposing cb this way with a tile in between makes it easy to read. Instead, we should
arrange the tiles like zcbcv
Person reading
It’s very dicult
3
to form an impression of an opponent without playing many matches. It’s best to
use long-term data (especially simple things like deal-in rate and riichi rate) and not rely on one’s
own experience since it’s prone to bias. In general, we also shouldn’t change our playstyle too much
in response to opponents. A lot of so-called “occult” styles are based on bias from focusing on one
particular case too much. However, if opponents have “tells” like getting visibly nervous when in
tenpai, we should exploit those. Many people think that a digital playstyle is easy to read because
it’s consistent, playing the same move in the same situation. However, playing dierent moves in
the same situation is always a loss some of the time even if opponents can’t read us. Furthermore,
playing consistently will let us think of what to discard and what to call in advance, making it
easier to play smoothly and reduce tells.
3
Long form shitpost abbreviated, also note that the author is talking about competent (JP) players, when playing
against chinks and /mjg/ shitters you can get a lot of information from their rank and >reputation (watch out for
novice smurfs especially :^)
Chapter 4
Point situation judgment
Principles of point situation judgment
In many mahjong rulesets, uma and oka exist.
1
Accordingly, round expected value is not always
equal to hanchan expected value. For example, when leading in all last, it’s common to go dama
even when we would otherwise call riichi to secure 1st place. In general, we need to be aware of our
placement at the end of the hanchan. The amount of riichi sticks and honba, as well as shuugi can
also inuence decisions. We’ll discuss how to adapt round expected value maximizing strategies to
these rules.
Rate has no impact on strategy but its ratio does The size of the rate (how many ¥ we
get per money point) is claimed to inuence strategy by many people. At low rate, its doesn’t hurt
as much to lose, so people prefer to have fun rather than to win is one line of thought. However,
if we want to tryhard win, we want to maximize hanchan expected value, which is independent of
rate.
However, the ratio of the rate (whether the uma is 10-20 or 10-30, how much the oka is,
how much the shuugi are) does have an impact on strategy. In rules that have a big reward for
taking 1st, we can make riskier plays at 1st that might lower our placement and vice versa. Other
examples are online clients that ignore points and only record placement, shizu-uma (uma that
changes depending on how many players are over/under a certain score) and tournaments where
only certain placements advance or the sum of multiple hanchans is important.
The point situation becomes more important closer to all last This should be fairly obvi-
ous. While ideally we should maximize hanchan expected value, which is a combination of expected
end score and expected placement, this chapter will focus on maximizng expected placement as it’s
easier to understand.
1
What the fuck are these? Uma are extra points that 4th and 3th pay to 2nd and 1st at the end, commonly
10-20 or 10-30 (in money points: each player gets base money points equal to (his score - 30000)/1000). Oka is a
bonus for rst place, usually of 20 money points, since players start at 25000 but the end score is calculated with
respect to 30000 points. The dierence goes to the winner.
147
148 CHAPTER 4. POINT SITUATION JUDGMENT
How to think about expected placement
Placement expected value formula
placement EV =
4
X
n=1
(placement points for nth place) × (probability of coming nth)
In all last, we can use this formula to determine whether it’s better to push or to pull among
other decisions.
Placement points depending on ruleset
25000 start, 30000 end, uma 10-20 35/5/-15/-25
25000 start, 30000 end, uma 10-30 45/5/-15/-35
MFC hanchan league 2/1/-1/2
MFC tonpuu league 1/0/0/-1
Tenhou 5th dan tokujou table 75/30/0/-105
When playing in tourneys with a prize pool or when yakitori
2
or busting out prizes exist, we
can adapt the formula to include them too. Since expected placement is an important strategy
concept that’s very likely to change depending on ruleset, we should endeavor to always remember
the rules and adapt to them.
Scoring techniques
To know our expected placement, we need to be able to score hands quickly in our head.
3
It’s not
necessary to memorize all the possible fu values. We only need to memorize 20 fu, 25 fu and 30 fu.
Then 40 fu, 50 fu and 60 fu are double those, and 70 fu is just 50 fu + 20 fu and so on.
Point dierence calculation
Suppose we need x points to improve placement
Then we can ron x points o any player
Or get a x/2 direct hit
Or with tsumo
Get a 4x/5 tsumo if neither we or the opponent are dealer
Get a 3x/4 tsumo if we’re the dealer
Get a 2x/3 tsumo if the opponent is the dealer
This is an easy to remember 1, 4/5, 3/4, 2/3, 1/2 progression.
2
Extra payment to opponents after not winning a single hand in the entire hanchan
3
Learn to score NOW if you haven’t already. Ask in the thread for good practice programs
149
For each riichi stick in play, reduce x by 1000 beforehand.
For each honba, reduce by 300 for ron o another player, 400 for tsumo, 600 for direct hit.
A similar but inverse process can be used to calculate how big of a point dierence a particular
win will make
No-ten payments induce a 4000 point dierence with 1 or 3 players tenpai and 3000 with 2
players tenpai
How to ght in all last
After all is said and done, the “daigomi”
4
of mahjong is risking it all in all last.
In standard 25000 to start 30000 to end rules with 10-30 uma, improving our rank from 4th to
3rd or from 3rd to 2nd is worth 20000 points, from 2nd to 1st 40000 points. 3rd to 1st is worth
60000 points. This is more than a yakuman which doesn’t change placement.
In 4th, we can’t lose placement anymore. Therefore, situations where we should content ourselves
with being last really don’t exist. It’s annoying to the other players, but in the long run, settling
for last is like strangling our own neck.
What we should pay attention to is that relying on luck to improve placement and then
being unlucky is no problem. There are many players who hate to rely on ura dora for a
comeback, or get disappointed when the ura doesn’t come.
But please consider the following. Mahjong is a game of chance. When making our hand, we
rely on the luck of the tsumo. It would be funny to treat ura dora and ippatsu dierently. Because
ura dora exists, we must take it into account. Should we rely on ura dora or take the hand that’s
certainly expensive enough? We should compare the probability of improving placement and decide
from there. If we’re missing 1 han to a certain comeback hand, there are quite some cases where
we can get it:
At least one ura dora (roughly 30% of the time)
Ippatsu (roughly 10%)
Direct hit
Kan into dora or extra fu
Another opponent declares riichi, giving us one more stick
All in all usually at least 40%, often more than 50%. Is the success rate of declining ron and
getting tsumo or declining tenpai to make a better hand as high? Usually not.
However, if we can make a guaranteed comeback hand, we should take it even if the wait is
worse, since the win rate of a bad wait is about 2/3 of a good wait.
Similar strategies can be used when calling. If calling would net us a conrmed comeback hand,
it’s ne to call aggressively even into atozuke or kata-agari hands. In all last, players will often
push everything which makes calling especially eective.
4
醍醐味 daigomi (n): 1. the real pleasure (of something); the real thrill; the true charm
2. avour of ghee; delicious taste
3. Buddha’s gracious teachings (Buddhist term)
150 CHAPTER 4. POINT SITUATION JUDGMENT
We can call even with 1 han less than needed and hope to add an aka or omote dora, create
another yaku or call kan. If we think the hand would be dicult to complete closed, we should
make calls like these.
Declining wins in all last
A situation that often comes up is when we call riichi in all last, and our winning tile comes out
from the wrong opponent, so that we’d need ura dora to come back if we call ron, but will certainly
come back if we can tsumo.
The chance of getting ura dora is about 30% (depending on the number of unique tiles in the
hand). If we don’t care about losing placement (currently 4th), we should decline if the chance of
getting tsumo is higher.
Of course, this depends heavily on the turn and on how many of our winning tiles are left. Also,
we must take into account that an opponent might win before we can tsumo. We therefore need
that
(1 opponent win rate) × tsumo rate > ura dora rate
We’ll assume that East and South get 18 draws, while West and North get 17, so we should add
1 turn to the values given here if in West or North.
With a bad wait, the tsumo rate with 1 tile discarded is only 36.8% even on the 1st turn. Taking
about 10% for opponent win rate, we should always declare ron with a bad wait.
With a ryanmen, the calculation is more dicult. Assuming all opponents fold, it’s good to
decline with 7 tiles and 4 draws left or 5 tiles and 5 draws left. However, if an opponent cut our
winning tile, it’s safe to assume at least one opponent is attacking. If we assume one opponent is in
tenpai (with a good wait 2/3 of the time) and the other two fold, we should only decline if we have
at least 12 draws left. If we assume the folding opponents will deal in 10% of the time, we should
always call ron. If we assume the attacking opponent is not yet in tenpai, it’s good to decline with
a good wait until about the 13th turn.
However, we have disregarded the possibility of losing placement or a renchan completely, so in
practice deciding will be more dicult, but we can use the same kind of reasoning, knowing that
the chance of ura dora is roughly 30%.
Speed maximization techniques
Often, we won’t care about score in all last (when we get 1st with any win).
When this is the case, we need to build our hand to maximize speed. Dora and its neighbors
suddenly become worse than regular tiles since they come out harder. All yaku after the highly
important rst one become unnecessary. However, going for no yaku riichi is not a problem either.
We’ll have to make plays that maximize win rate to the utmost.
Example qqetuidgjkkcbmdora q cut qand go for tanyao
Since we want to maximize win rate, we should go dama if we have a yaku. However, we
should take a good wait no yaku riichi over a bad shape dama.
Example rtyyyzzxvbnm,. cut x and riichi
Example tyyyzxccvbasd4 cut 4 and riichi!
151
However, in the lower example, if calling riichi would lower our placement, we should stay dama.
Other useful plays are those that upgrade the shape, ignoring score
Example eerrty cut e to make sanmenchan with u over iipeikou
Example wrtyudfgggbnm call any of tyisg
Example uuiiaaas
s
s7
7
7 chii yo
However, when playing with rulesets where raw points or shuugi are important, we don’t need
to maximize speed as much.
When to attack fast
There are other situations where a swift attack is useful, such as
Slim point dierence both upwards and downwards
Improving placement by 1 is easy, but improving by 2 is unrealistic
Improving placement is unrealistic, but there’s a slim dierence downwards
We want to avoid yakitori
Often, we should emphasize preserving our placement over improving it when being overtaken
is likely. While people often say “in mahjong, take 1st at all cost” and there is some truth in this
(rulesets where 1st place gets a big reward are common), it’s no use to chance an impossible 1st
place.
With standard 45/5/-15/-35 placement points, players who get 30%/20%/20%/30% (average
rank 2.5) results and those who get 26%/26%/24%/24% (average rank 2.46) will make the same
amount of money. It’s both much easier and much more eective to improve average placement by
0.05 than to improve top rate by 5% (this is extremely hard). To raise expected placement,
rather than chase many 1sts, it’s much more eective to slightly increase average
placement by preserving placement when going for 1st is unreasonable.
Calling when a comeback is uncertain
When we get 1st with any win, we should of course call from anywhere maximizing speed. Then
what about the following situation?
If we call, we get an uncertain comeback (needing to tsumo or win with a particular tile), if we
stay closed or calls something else, we can make a comeback with a win from anywhere.
The situation is similar to the theory of waiting for an upgrade we discussed earlier (a hand we
can only win under certain conditions is like a bad wait or a furiten). Accordingly, if no opponent
is yet in tenpai, we should decline the call if we can draw at least 7 kinds of tiles that
would give us a conrmed comeback hand. Of course, if an opponent is already tenpai, we
should take even a bad tenpai to catch up.
Problem 6th turn, dora 4, 1300 point dierence with 1st place (non-dealer)
wwrrpxc
m
,. 7
7
7
152 CHAPTER 4. POINT SITUATION JUDGMENT
If we draw or call pon on wr, we can only get 1st with tsumo, but with any of eyzv
tsumo or chii (so 8 types), we can win from anywhere. Accordingly, we should not take tenpai with
wr.
Push-fold judgment in all last
Placement points of course have a big inuence on push-fold judgment.
Suppose that under standard rules (25000 start 30000 end, 10-30 uma, so 45/5/-15/-35), we’re
in 2nd while an opponent has called riichi, and that if we win, we will certainly be rst, but if we
deal in, we’ll certainly be last. When should we push in this situation?
Since both of these scenarios represent a change of 40000 placement points, we should push if
win rate > deal-in rate. Even if they’re the same, we should push since the opponent might tsumo
and lower our placement. Since this will be the case even with a bad wait tenpai, we should attack
with all but the most dangerous tiles.
The decision gets more dicult in iishanten. With a wide iishanten (about 20% chance to draw
into tenpai), we should push, but with a narrow iishanten (about 10%) it’s no problem to fold.
The probability of an opponent tsumo or opponents dealing into each other is dicult to estimate
making push-fold judgment in all last very complex. We can gure out which opponents will push
or fold not just from their discards, but also from their placement and point dierence (last place
will push, an opponent who can’t realistically lose placement will also push, 1st place with a big lead
will often fold). In general, we should start by thinking how much point each placement is worth,
then estimating the chances and eects on placement of winning, dealing in, opponents dealing into
each other and getting tsumo, and weighing the relative expected placement points of pushing and
folding from there. Since it takes a lot of time to estimate all of these variables, we should start
thinking about this as soon as all last starts.
2nd place, winning gets us 1st, dealing in gets us 3rd but certainly not last
We should attack even if win rate/deal-in rate = 1/2, so with any iishanten or even a good 2-shanten.
Conversely, if we can’t get 1st and can get 4th, we shouldn’t attack unreasonably. Even if folding
would certainly get us 3rd, we should still only push if win rate > deal-in rate.
1st place in tenpai and an opponent is also in tenpai
If the opponent is a non-dealer and we can read that dealing in will let us keep 1st, we should
attack. If we are under threat of losing 1st place from the other 2 opponents and our hand is
slow to tenpai, we should even deal in on purpose (if our hand is fast it’s better to attack). While
reading the wait is hard, it’s not hard to discard tiles that are safe against the other two opponents
but not against the third. Even against riichi, it’s rare to deal into a baiman (or haneman when
playing without aka) so it’s not necessary to fold against a non-dealer if we’re safe against such
a deal-in and threatened by the dealer. However, if we’re playing in a system where raw points
impact results, we should almost never deal in on purpose.
If dealing in would drop us to 2nd, while a tsumo or ron of another opponent would let us keep
1st, we should usually fold even from tenpai. On the other hand, if we aren’t safe against a tsumo,
we should push unless just it’s before a draw and we’re safe against no-ten payments.
153
If dealing in would drop us to 3rd, we should push with a good wait until the mid game and
with a bad wait in the early game. If dealing in would drop us to 4th, we should only push with a
good wait in the early game and otherwise fold.
Push-fold judgment one hand before all last
Since our placement in South 4 is very important, thinking ahead to our possible placement there
will also inuence our push-fold judgment in South 3.
Since losing 2 placements in South 4 without dealing is quite rare, there is a strong correlation
between our placement after South 3 and South 4. Improving our placement in South 3 even by 1
place therefore has a big impact on nal placement.
However, we shouldn’t focus on “being rst at the start of all last” too much. If we have dama
3900 in South 3 and 1st place is ahead by 2000, we can indeed get 1st place with dama ron from
anywhere. However, we’ll only have a 1900 point lead which is very easy to lose, so we should riichi.
The same is true if we have a small lead in South 3.
Same as in South 4, it’s no problem to rely on luck to improve placement in South 3, especially
since we’ll get another chance in South 4.
It’s also often possible to win a cheap hand in South 3 that will narrow the gap to make it easier
to come back in South 4. For example, if we’re West in South 3 and trailing 10500 behind rst
place North, we need a haneman ron on someone else or haneman tsumo. However, if we win a
1000 point trash hand now, we can take 1st with just a mangan tsumo next round. Getting mangan
tsumo is much easier than haneman so this is quite important.
What has been said about all last can be used in South 3 too, but to a lesser degree. We
especially don’t need to be severe in attacking with bad hands. If we’re last place in South 3 and
our hand is fucked, it’s ne to sit the hand out.
How to make mangan
The most useful skill in all last is making the fastest possible hand, since 1/4 times we’ll be 1st
(even more if we count all the cases where we want to attack at maximum speed). The second most
useful skill is how to mangan, since situations where we’ll need a mnagan to improve placement are
common and mangan is often a realistic goal (unlike haneman and above).
However, if we’re 2nd and need a mangan to overtake 1st, while 3rd and 4rd can overtake us
easily, we should go for mangan only if we get lucky draws and attack quickly with a cheap hand
otherwise. Conversely, if the players below can’t overtake us even with a mangan tsumo, we can
go for a comeback hand. Even if we’re dealer, we should try to go for one big strike than hope to
chain renchan.
154 CHAPTER 4. POINT SITUATION JUDGMENT
Since we can’t get overtaken even with a mangan tsumo, we should cut 5and aim for mentanpin
(with sanshoku or aka if we get lucky for a guaranteed dama comeback). If the players below us
were close, we’d also cut 5, but this time we’d call anything and go for open tanyao.
The key to chasing mangan is dora. If we have dora 3, we only need 1 more yaku, so we should
call everything if we have one. If we have a dora pair and can call, it’s also usually no problem.
Since we can get a 3rd omote or aka dora or make another yaku, we’ll end up getting mangan
more often than when staying closed. If we have a single dora, we should hold on to it even if it’s
dicult to use. If we draw a second one, we can get mangan with just riichi and tsumo, or even
with riichi tsumo dora 1 ura 1 if we don’t. If we have no dora, it’s usually good to try to make a
closed yaku like tanyao or iipeikou (+ riichi tsumo ura 1) and hope to draw dora on the way. Of
course, we should be aware of sanshoku and ittsuu, but it’s not needed to break up groups to chase
them unreasonably.
However, there are hands where even reaching closed tenpai, not to mention winning a mangan,
is very dicult, for example if the hand is slow and has no dora or visible yaku (or the dora is
completely useless). In hands like these, we should accept that it’s unreasonable and go for a forced
honitsu (especially with an honor dora) or chinitsu in the suit we have most of.
5
We can especially
make aggressive calls like this if we’re unlikely to be overtaken.
5
The author seems to have forgotten about the shortcut to haneman. Chiitoi can be very powerful, but without
dora, requires riichi chiitoi + 2 (ura or tsumo + x) to make mangan, which is quite hard to pull o (remember that
chiitoi has a lower chance of hitting ura than other hands).
155
What to do when far behind
Hanemam needed for comeback
If we need at least haneman, we’re in for trouble. While aka help a bit, it’s still no easy task. The
most common and easiest to make haneman are mentanpin tsumo dora 2 and mentan/menpin
tsumo dora 3, so ecient closed hands. If we have few dora, we can think of stacking iipeikou,
sanshoku, ittsuu with pinfu, and if we still end up at mangan we can hope for ippatsu, ura
or a direct hit. The easiest open haneman are chinitsu + x, honitsu yakuhai dora 3, toitoi
yakuhai dora 3 and the like. If we have no other option, we can go for riichi tsumo chiitoitsu
dora 2 as a last resort. Since we’re likelier to get ura than draw dora if we don’t have any, we
should instantly riichi with chiitoi only if our wait looks drawable.
If we aren’t last place and need a haneman to improve placement, we should usually not chase
it unless our draws are excellent and focus on not getting overtaken. If we need to avoid all last
and need a baiman or more while our hand won’t allow it, we should try to secure no-ten payments
to narrow the gap or deal into the dealer for a renchan as a last resort.
Settling for last
If even a haneman tsumo isn’t enough, or our hand is too bad for this hand, and we are certain the
match will end after this round, what should we do? If playing in a placement system, we should
go for even the slimmest chance at a comeback. However, if raw score or other factors (shuugi,
yakitori etc.) play a role, it’s a dierent story.
If the chance of our placement changing is negligible (for example also if we’re rst place dealer
with at least a 30000 point lead), we should just maximize winnings from this round, so play just
like we would in East 1.
How to play when a player is close to shadowrealm
The hanchan can also end before all last if a player runs out of points. Therefore, if someone is
close to busting out, we should play with the same intuition as we would in South 4. If we’re close
to busting out ourselves, or 3rd when an opponent is close, we should attack unless we have a weak
hand and want to bet on a draw. If shadowrealming an opponent with dama would net us 1st and
calling riichi would make him fold, dama is eective. When deciding whether to decline a win from
someone else, we can think in the same way as we do in all last.
In mahjong, any lead no matter how big can be overtaken, so the advantage of ending the
hanchan is big. Even if we already have a lead or it’s still the East round, we should assertively try
to shadowrealm an opponent to end the match. For example, if haneman tsumo would shadowrealm
someone and let us overtake 1st place while we have a mangan tsumo dama, we should riichi even
with very few draws left. It’s no problem to decline a ron o the wrong player here. If we’re rst,
we’ll want to fold more, but if we have a shadowrealming hand we’ll want to counterattack (of
course without declining wins).
If a ceiling (hanchan ends when a player gets more than x points) is in play, the same ides apply.
Riichi sticks and honba
Sometimes we’ll play dierently because of riichi sticks and honba. Especially in rules where each
hinba is 1500 points their inuence is big. While winning fast becomes more eective with more
156 CHAPTER 4. POINT SITUATION JUDGMENT
sticks in play, it’s not that important to change our playstyle too much. For example, we should
still call riichi with good waits below mangan. In general, when there are many sticks, win rate
becomes more important.
Example With 3 riichi sticks, we can push against riichi even with 1000 good wait.
Example When unsure about whether to call riichi with a good wait mangan in the mid game,
we should stay dama if there are 2 riichi sticks.
When to call kan
Basics
The player most likely to reap the blessings of kan is the one closest to tenpai. Therefore, we should
call kan if we think we’re that player.
6
If there’s an opponent equally close to tenpai, we call can
kan only if the added points would benet us more.
When opponents are no-ten
If we’re in tenpai. (If we have an open mangan where one more dora wouldn’t give us haneman,
it’s dicult. If the extra draw is important, call ankan and kakan. If exposing part of the
hand would make opponents too wary, lowering win rate, don’t ankan or daiminkan. If not
calling kakan would throw o opponents, we can decline it too. But if the gain from a dora
would be big, we can call kan even at the cost of scaring opponents.)
Good shape 1-shanten in the early or mid game.
Very good shape 2-shanten in the early game, for example rtyyaaaafjjccv
When an opponent is in open tenpai
If we’re in riichi, kan.
If we’re in open tenpai, kan when win rate > deal-in rate. Even with a bad shape, kan if the
point increase (39005200 etc.) is big.
Don’t call kan in no-ten.
When an opponent has called riichi
If we’re in riichi, don’t kan if we have a bad shape and the tile is safe. Otherwise kan.
If we’re in open tenpai, call closed kan on a dangerous tile. Otherwise, don’t call kan unless
the point increase would be big (39005200 or 8000)
Don’t call kan in no-ten.
Together with these basic rules, we should adjust a little for point standing (kan less when in
the lead and vice versa). However, it’s still ne to kan in tenpai when in the lead for the extra
draw. Conversely, we shouldn’t call kan if our hand is fucked even when we’re losing.
6
This is the old theory. The modern theory is to call kan whenever we feel our chance of winning the hand is
bigger than 1/4, for example with a callable 3-shanten in the early game.
157
Using kan components
When we decide not to call kan (yet), we should get of rid of the 4th tile if we don’t plan on using
it and we have a more useful tile. The benet of a faster hand is often bigger than that of kan.
Similarly, we shouldn’t call kan of doing so would hurt the hand.
Example qwetyujjjjcvm, don’t call kan
Cutting j guarantees a good shape tenpai with xvn..
Example wrtttpuilllcvbdora w call kan
While we lose a good shape if we draw yo, we can go for e kanchan for 6400 or mangan
dora tanki, while if we didn’t call kan and cut w into ryanmen tenpai we’d only get 2600. So we
should kan.
Exceptions
We should also call kan when:
The extra fu would give us a conrmed comeback in all last
We can steal the haitei from an opponent in riichi
We’re last in all last and don’t care about losing points
When an opponent dealing into a big dick hand or the dealer getting hit by a big tsumo would
improve our placement in all last