Ippatsu

Ippatsu (一発)

Ippatsu is a one-han yaku (scoring hand) in mahjong that rewards a player for winning within one complete turn cycle immediately after declaring riichi, up to and including that player’s next draw.

Ippatsu in detail

Ippatsu, literally meaning “one shot” or “one chance,” is a time-sensitive yaku that adds value to riichi declarations. When a player declares riichi, they lock their hand and can only win by tsumo (self-draw) or ron (claiming a discard). If they win within the uninterrupted go-around after the declaration, up to and including their own next draw, they earn the ippatsu bonus.

The critical condition for ippatsu is the timing of victory. The turn cycle must remain unbroken by any call. If any player calls pon, chii, or kan during this cycle, ippatsu is immediately negated and cannot be scored, even if the riichi player wins on their next possible draw or claim. This makes ippatsu a somewhat fragile yaku that depends on other players’ actions.

Activation Requirements

To score ippatsu, all of the following must be true:

• The player has declared riichi on their most recent turn
• The player wins (by tsumo or ron) before their next turn
• No call of any kind (pon, chii, or kan) has been made by any player since the riichi declaration
• Riichi has been declared, which itself satisfies the one-yaku requirement; no additional yaku is needed for ippatsu to count

Interaction with Kan

The kan restriction is the defining feature of ippatsu. Unlike most yaku that persist throughout a hand, ippatsu has a built-in expiration tied to game events. A player declaring kan, whether it’s a closed kan, open kan, or added kan, immediately cancels ippatsu for all riichi players waiting to win. This mechanic adds strategic depth, as players must weigh the value of calling kan against potentially giving opponents ippatsu opportunities.

Scoring Value

Ippatsu is worth exactly 1 han, making it a modest but meaningful addition to a winning hand. In practical terms, it often converts a hand that would be worth 1,000 points into one worth 2,000 points (at minimum), or upgrades a larger hand by one tier. While not as valuable as yaku like tanyao or yakuhai, ippatsu represents a bonus for aggressive, timely play after riichi.

Ippatsu in practice

A player in East position declares riichi on their turn. The South player discards, West player discards, and North player discards without calling kan. When the turn returns to East, they draw a tile that completes their hand for a winning tsumo. Because they won before their next turn and no kan was called, they score ippatsu (1 han) in addition to any other yaku in their hand, such as the riichi itself and tanyao, for a total of 4 han once menzen tsumo is included.

Alternatively, if after the riichi declaration the South player calls kan on their turn, ippatsu is immediately cancelled. Even if East wins on the very next draw, they cannot score ippatsu, they can only score the other yaku present in their hand.