Who pushes against the leader? South 4 game theory
The dealer in 1st riichis in All Last, and each trailing player waits for someone else to push. Here's how the scoreboard picks the volunteer, and where sashikomi turns into kingmaking.
戦術
Strategy
Riichi mahjong strategy from a pro in Japan: how the scoring rules decide your best play, when to chase 1st, and when avoiding 4th matters.
Facing two tenpai hands: triage your defense
The dealer riichis, then a second player chases, and you can't fold to both with every tile. Here's how to sort the two threats like a field medic, and the Houou numbers that decide who gets your safe tiles.
Pro mahjong's main rules have no red fives
The JPML's official rule has no red fives, no ippatsu, and no ura dora, and the NPM and Saikouisen skip the red fives too. Here's each rulebook side by side, and what riichi is worth when it only buys one han.
Goodhart's law in mahjong: when your deal-in rate lies
A low deal-in rate looks like skill. Fold every hand and it drops while your placement falls with it. Here's why deal-in rate, win rate, and AI match rate all break once you chase them, and the two numbers that don't.
Riichi is a loser's game until you reach Houou
Below the top rooms, placement is decided by the tiles you throw, not the hands you build. Charles Ellis called that a loser's game. Here's what it costs in points, where it ends, and the ten-hanchan log that shows your own unforced errors.
Riichi wait win rates by turn: suji traps, honors, and dama
A two-sided wait declared on turn 8 wins 52% to 57% of the time at Tenhou's top level. A wait on a 5 wins 33%, or 46% behind a suji trap. Here's how often every common wait wins, turn by turn, and when dama beats riichi.
How dangerous is the dora? Riichi and open-hand deal-in odds
When the dora is a 5, 11.5% of riichi hands at Tenhou's top level are waiting on it. An ordinary 5 sits in 8.0% of riichi waits. Here's the dora's real danger by tile, by wait shape, and against open hands.
Honor tile discard order in riichi mahjong, seat by seat
Guest winds go first and your own wind goes last. The round wind, the dragons and the isolated terminals sit in between, and each has a reason. Here's the full order for every seat, and the hands that break it.
Tenuki: when to ignore a riichi and keep building
Go players have a word for not answering a threat because your own move is bigger. Riichi mahjong needs it. Here's when a riichi is a threat you ignore, when it's one you answer, and the Tenhou numbers that draw the line.
Target fixation: dealing into the player you ignored
A riichi goes up and every eye lands on that pond, so the quiet two-call hand on your left rons you. Here's why attention locks onto one threat, the Houou odds on the hand you ignored, and the scan that catches it.
Is the open hand tenpai? Tenpai odds by calls and turn
An opponent with two calls on turn 8 is tenpai 53% of the time at Tenhou's top level. One call, 27%. Three calls, 88%. Here's the full table by calls and turn, by hand type, and the discards that move the odds.
All Last math: your real odds of finishing 4th by score gap
Start All Last in 3rd, less than 1,000 points above 4th, and you finish 4th 35% of the time at Tenhou's top level. Make the gap 4,000 and it's 18%. Here's the full table by score gap, seat, and who's the dealer.
What folding in riichi mahjong costs: 1,100 to 1,900 points
Folding against a riichi isn't free. Tenhou's Houou logs put the price at 1,100 to 1,900 points a hand, by turn and seat. Here's that price next to what a deal-in costs and what a chase wins, and the hands where paying it is right.
Mahjong zugzwang: what to discard when nothing is safe
A riichi is up, nothing in your hand is genbutsu or suji, and you still have to discard. Here's the order of least-bad tiles from the Houou data, a worked fold with no safe tile, and the two exits chess never had.
Winning riichi mahjong: calculating your chances
Skilled pros only take first place 30% of the time. Whether that counts as winning depends on your rules, so here's how to find your win condition and play for it.
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