|Kanji||立直 or リーチ|
|Value||1 han (closed only)|
Riichi (立直 or リーチ) 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.
When a player has a closed tenpai hand, the player may declare riichi. Doing so gains the hand 1 han. To declare riichi, a player announces riichi and 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 for an open meld, then the next discard is turned sideways as a replacement.
Unless the first sideways discard is claimed for a win immediately, the riichi announcer now places a bet of 1,000 points on the table. This bet is collected by the next player to win a hand. Specific rulesets may handle differently what happens to the bet on a multiple win.
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.
It is not allowed to declare riichi when less than four tiles remain in the wall. The player must be able to draw one more tile in an uninterrupted set of turns.
Ippatsu (一発) is awarded if the player receives a winning tile within an uninterrupted set of turns after the riichi 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. Ippatsu is a yaku worth 1 han.
Double riichi (ダブルリーチ) is a special case for riichi, where the player declares riichi on the first turn. No tile call may have interrupted the turn order before the declaration, where applicable. Double riichi is worth 2 han instead of 1 han, as a bonus for the initial timing.
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.
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.
If a riichi declarer does not win at first opportunity, he will be permanently furiten.
When a riichi declarer wins, he may flip the tiles underneath the dora and kan dora indicators. These flipped ura dora indicators may increase the value of his hand.
Any closed hand becomes eligible for winning by ron.
Kans formed by any player provide two extra dora indicators for the riichi declarer instead of one.
It is less likely for opponents to deal in. In addition, it is impossible to change the composition of the hand in order to get a better wait or an improved score.