Ippatsu

Ippatsu

Type	Yaku
Kanji	一発
English	One shot
Value	1 han
Speed	Riichi dependent
Difficulty	Luck

Ippatsu 「一発」 is a yaku that is completely dependent on riichi. After declaring riichi, if the player wins before their next discard, and before anyone makes a tile call, ippatsu is scored. You must declare riichi to score ippatsu, so a hand can never have ippatsu by itself.

While ippatsu is generally considered to be a standard yaku, certain rulesets do not use it, in order to reduce variance and lower the value of a riichii. In general, when sitting down to play a game, ippatsu is counted unless otherwise specified or agreed on before the game.

Development

In order for ippatsu to be counted, the hand must win before the hand in riichi discards its next tile. The earliest possible chance to win with ippatsu comes from the shimocha's discard (player to the right). The latest possible chance to win with ippatsu is with the player's next drawn tile after the riichi declaration.

Furthermore, no interruption to the turn must occur. This means that tile calls will immediately end the chance for ippatsu. This includes any calls for kan except for a robbed kan (chankan). In sanma, the call for kita also denies ippatsu. If the riichi player declares kan or kita, ippatsu is still denied.

To repeat: even if a hand is won before the next discard, if a call is made, ippatsu is denied. Thus, players can purposefully make tile calls in order to disrupt another player's chance for ippatsu.

Examples

Jigoku ippatsu tsumo by Pekora.

• Ippatsu after kan.

Kan is called prior to the riichi call, and the hand wins on the next draw without interruption, so ippatsu is scored.

• Ippatsu on discard

This hand wins on a discard before the next draw.

Ippatsu nullified

• Ippatsu blocked by tile calls

In this example, the hand wins from an opponent discard before the next tile draw. However, two tile calls were made prior to the win, so ippatsu is not scored.

Compatibility

Main article: Yaku compatibility

RCH

DRI

IPP

SMO

TAN

PFU

IPK

ITT

YAK

SDJ

SDO

TOI

SNA

SNK

CHA

JUN

RPK

SSG

HRO

HON

CHN

CHI

RIN

HAI

HOU

CHK

IPP

Ippatsu requires riichi (or double riichi), so it is impossible for a hand to score with ippatsu alone. At the very minimum, a hand could be riichi with ippatsu. Riichi and ippatsu are scored as separate yaku.

Unlike riichi, ippatsu cannot be combined with two yaku: rinshan kaihou and houtei raoyui. Rinshan requires a kan call (after declaring riichi), which would invalidate ippatsu. As for houtei, a riichi declaration must be made with at least 4 tiles left in the live wall. That leaves the very last possible tile draw (and discard) belonging to the riichi declarer.

Note that chankan is compatible with ippatsu. When winning off chankan, the kan call is interrupted, so ippatsu is retained.

With haitei

Winning hand of ippatsu haitei in M.League.

The last possible chance for riichi comes when there are eighteen tiles left in the walls, counting the fourteen tiles in the dead wall. That leaves four tiles left for regular player draws. After the last possible riichi, if no tiles are called, every player would have exactly one tile draw left. Therefore, the last tile would go to the riichi declarer, allowing both ippatsu and haitei to be scored. Naturally, players may make tile calls to disrupt both yaku.

External links

• 一発

Ippatsu in Japanese Wikipedia