Toitoihou

Toitoihou 「対々和」, often shortened to toitoi 「対々」 is a standard yaku. Known as "All Triplets" in English, toitoi requires all four tile groups to be either triplets or quads.

Toitoihou

Type	Yaku
Kanji	対々和 対々
English	All triplets
Value	2 han
Speed	Medium
Difficulty	Easy

Tile pattern

Agari: or

Agari: or

Closed toitoi

Ron: or

If this hand wins by tsumo, then it counts for the suuankou yakuman. Otherwise, it's a toitoi mixed with sanankou.

Formation

As the name implies, this yaku requires koutsu. Usually, this yaku is called open due to the ability for pon to claim discarded tiles from any player, giving this yaku the nickname of "pon palace". This yaku does not reduce in value once opened.

Viability

Naturally, this yaku is reasonable if your hand contains many triplets and/or pairs. Note that toitoi looks easier than it actually is. There are only 2 possible tiles that can turn a pair into a triplet - there are 4 copies of a tile in mahjong, and 2 are used in the pair, leaving 2 tiles that can make the pair into a triplet. Meanwhile, a ryanmen joint can be turned into a sequence with 8 possible tiles. While you have access to pon to turn pairs into triplets, your opponents might not discard the tiles you need to pon in the first place. The tiles could be in the dead wall, or they could be used in another player's hand.

Pairs made out of middle tiles (tiles from 3-7) are particularly hard to pon. Because the middle tiles are likely to be kept in an opponent's hand, they are hard to pon. If you have multiple pairs made out of middle tiles, this yaku becomes slower to complete.

In addition, a hand with many pairs can also form chiitoitsu. The (very rough) rules of thumb are:

• If you have 4 pairs and one turns into a sequence or triplet, you should probably go for a regular hand structure. This may or may not be toitoi.
• If you have 5 pairs, you should likely go for chiitoitsu. Keeping the option for toitoi is fine (e.g. 4 pairs, 1 triplet, 2 lone tiles. The hand can turn into chiitoi if you discard the triplet, can toitoi if you pon) so long as the pairs are reasonable to pon.
• If you have 4-5 pairs, and one of the pairs cannot be turned into a triplet, because both remaining tiles of the pair are visible, then favor chiitoitsu.

Compatibility

Main article: Yaku compatibility

^ Ippatsu requires riichi to be of any use.

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

TOI

Toitoi is incompatible with any yaku requiring a sequence, meaning pinfu, iipeikou, ittsu, sanshoku doujun, ryanpeikou, and chankan (since it can only win on a sequence wait). It also cannot be combined with chiitoitsu, since it doesn't use mentsu.

Toitoi with mentsumo and junchan actually form yakuman, as suuankou and chinroutou respectively. Toitoi with chanta forms honroutou instead.

External links

• 対々

Toitoihou in Japanese Wikipedia