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, denitely
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 dierence once you start playing. You just start thinking about the tiles dierently after a
while.
The book is heavily focused on tile eciency, 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 eciency, 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 eciency 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 eciency 9
Principles of tile eciency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 eciency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Head start riichi judgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Win rate maximizing damaten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Defensive damaten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Wait improvement judgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Wait choice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
1.3 Calling eciency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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
Dierences 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 eciency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
The importance of being rst to tenpai . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Classication 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
Eectiveness 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 specic 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
Eective 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
Reex 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 eciency (includes score eciency, 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 eciency 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 eciency 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 eciency 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
dicult.
• 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 eciency of good hands,
whether to call riichi, how to fold, how to deal with opponents’ calls, how to evaluate score
dierences.
• 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 dierently 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 eciency
Principles of tile eciency
We will rst discuss the most important things we need to pin down.
By tile eciency, 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 dierence 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 backre, 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 eective tiles
When deciding what tile to cut, we should consider what tiles are the eective tiles of each tile. A
tile is called eective when, if we would draw it, we’d keep it and discard something else. If we’d
discard it, it cannot be called eective, 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 eectiveness (can make a joint, can make a group, can make a
joint into a better joint etc.).
However, among eective tiles, there is a clear dierence 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 backre y, we can cut u and make a wider iishanten. (Although tile
acceptance-wise, there is no dierence 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 dierence 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 eect.)
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 eect 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 dicult 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 eective tiles closer to tenpai.
1
Fundamental rule of tile eciency
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 eciency 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 eciency by the public), it is indispensable to learn tile
eciency 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 eciently create four groups and a head, it’s good to divide the hand into
groups and group candidates.
Classication 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 (嵌張): 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 sucient, if we have
3 or less, they are insucient. 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 dierent classes, or identically good shapes, or when several possible
ways to break up a complex shape exist, we’ll have to establish dierent criteria.
In this strategy guide, we hope to create an all-encompassing classication 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 dene 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 insucient 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 ecient to replace a weak joint with a better one, 2 and 3 are generally
inecient 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 dierence 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 inuence 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 dicult to turn into a set. If there is no
dierence, 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 dierence 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
dierence 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 <