Toitoihou 「対々和」, often shortened to toitoi 「対々」 is a standard yaku. In English, it is referred as "all triplets". That's due in part with every tile group to be composed of triplets. This hand is immune to any requirement involving the numbered suits or honor tiles. Simply, any group of triplets would suffice. In terms of han, this yaku is not devalued while open. Players, whose hands containing multiple pairs, may be encouraged to call on tiles to complete triplets. With in mind, this yaku also acquired the nickname of "pon palace".

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

Tile pattern

               Agari:   or  

Closed toitoi

              Agari:   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.

Compatability

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

Toitoit 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.

Viability

Naturally, this yaku can be developed when the start hand, or later subsequent tile draws, produces a number of pairs or even triplets. As the yaku requires, every tile group must be a triplet, which may be acquired via the tile draws or player discards (pon). However, if the hand happens to develop with a concentration of pairs (normally 4 or 5 pairs), then a player may actually opt to develop chiitoitsu instead. A hand with 6 pairs is already tenpai for chiitoitsu, which renders a chase for toitoi to be rather pointless.

External links

Toitoihou in Japanese Wikipedia