Chiitoitsu: Difference between revisions

'''Chiitoitsu''' {{kana|七対子}}, also known as '''chiitoi''' or '''niconico''', is one of the standard yaku hands. This hand consists of seven pairs, where no two pairs may be identical. In other words, every pair must be distinct.  Though some [[Yaku_variations#Chiitoitsu|house rules]] actually allow four of the same tiles to count as two pairs each. This hand is one of the two exceptions of the "four melds and one pair" rule of forming a hand, where the other exception is the [[kokushi musou]]. This hand is closed only.

Given the number of pairs in this hand, it is often tempting to call pon with matching discards to the pairs. However, it is generally noted that toitoi is actually a slower developing hand in this instance. This is especially the case, when the potential chiitoitsu hand sits at [[Shanten|iishanten]]; and it may actually be recommended to let the hand develop into a chiitoitsu [[tenpai]], rather than forcing [[toitoi]]. Tenpai for chiitoitsu always uses the wait of [[tanki]] (pair wait) in order to complete the seventh and last pair for the hand.

Nevertheless, transition to other yaku may actually be favorable, if the hand develops at least one [[ankou]]. In this case, players may find themselves looking to develop a toitoi hand, [[sanankou]], or even [[suuankou]]. Whatever the case may be, this consideration does take some discretion, particularly when taking into account the number of tiles available, current point standing, and/or number of tile draws remaining.

Finally, the pairs must be distinct.  A group of tiles forming ankan does not count as 2 tile pairings.  Some house rules actually allow four-of-a-kind to count as two pairs.

The composition of this yaku makes it very restrictive regarding its combination with other yaku.  Chiitoitsu cannot be combined with any yaku dependent on [[mentsu|tile groups of three]].  As the yaku demands, all tiles must be in pairs. Chiitoitsu combined with [[chanta]] gives [[honroutou]], and it cannot be combined with [[junchan]] as there are only six different terminals, but chiitoi requires seven distinct pairs.

As for [[rinshan]] and [[chankan]], this yaku may combine with neither. Rinshan requires a call of [[kan]], but that is not allowed with chiitoitsu. A player may draw all four of a specific tile, but they are not treated as distinct pairs.  For chankan, all chiitoitsu [[tenpai]] hands utilize [[tanki]], or single tile wait.  In order to win with a chiitoitsu hand, that single tile must be paired, and it is physically impossible for it to be used for an added kan call.

A chiitoitsu hand may collect sequential series of paired tiles.  The pattern would simply look like [[iipeikou]] or even [[ryanpeikou]].  For both of these yaku, neither are compatible with chiitoitsu.  Once again, all tiles are considered to be pairs, instead of [[mentsu|three-tiled-groups]].  For both iipeikou or ryanpeikou, [[shuntsu|sequences]] are required for completion, which simply does not fit the definition of chiitoitsu.  This is especially the case for ryanpeikou, which actually looks like a collection of seven pairs on its own.

High scoring chiitoitsu hands are possible without dora.  The highest possible involves [[riichi]], [[ippatsu]], [[menzenchin tsumohou|tsumo]], [[haitei raoyue and houtei raoyui|haitei]] and [[chinitsu]].  With the 2 han for chiitoitsu, the combination brings the hand to a whopping 12 han.  Note that [[tanyao]] cannot be added, as the hand 22334455667788 can be scored as [[ryanpeikou]] and [[pinfu]] for an additional 2 han over chiitoitsu. In some [[rule variations#Daisharin|rule variations]], this hand is an [[optional yaku|optional yakuman]], known as "daisharin", "daichikurin", or "daisuurin", depending on the suit..

All tiles in this yaku must be in pairs.  Therefore the dora tiles also occur in pairs.  If dora is involved, then at minimum, this yaku may possess at least 2 dora.  The notable exception are the red dora, which appear as individual reds in their own right.  [[Dora_variations#Akadora|Aka nashi]] games makes the red dora irrelevant, as they are unused.