Riichi

Riichi is the most commonly used yaku in the game. This yaku may apply to any closed hand and may be declared upon achieving tenpai. Due to its common usage, various specific game scenarios must be considered when using riichi.

Rules

After any time a player has a closed tenpai hand, the player may declare riichi. Upon doing so, the hand instantly gains the potential to win 1 han. To declare riichi, a player announces riichi and deposits 1000 points onto the table. Then the player discards a tile facing sideways in the discard pile. This is done to indicate when riichi was called. If that tile is claimed by another player, then the next discard is turned sideways as a replacement. After a riichi declaration, the hand remains locked and unchangeable. In this state, the player is simply waiting for a winning tile to appear, either by draw or discard.

Ippatsu

This yaku is awarded if the player receives a winning tile within an uninterrupted set of turns after the winning declaration. Tile calls interrupt the set of turns. The latest possible chance to win with ippatsu is with the player's next drawn tile after the riichi declaration.

Double riichi

Double riichi is a special case for riichi, where the player declares riichi with a dealt hand. In turn, the very first discard is the tile turned sideways.

Kan during riichi

When a riichi declarer holds three identical tiles and draws the fourth after the riichi announcement, he may form an ankan from these tiles instead of discarding the fourth. The hand composition and the possible winning tiles may not change: It is not allowed to declare kan if, for some possible winning tile, any of the three identical tiles may be interpreted as part of a shuntsu or part of the pair.

, draw:

It is not allowed to kan the fours. The manzu tiles may either be interpreted as a 3-4 ryanmen wait and a 4-4 pair, or as a 4-man ankou with a 3-man tanki wait. For a legal kan declaration, the three identical tiles would have to be an ankou in any interpretation. Had the player drawn a west wind, he would have been allowed to kan it.

, draw: