Chiitoitsu
| Type | Yaku |
|---|---|
| Kanji | 七対子 |
| English | Seven pairs |
| Value | 2 han (Closed only) |
| Speed | Medium |
| Difficulty | Medium |
Chiitoitsu 「七対子」, also known as chiitoi or niconico, is a yaku scored when a hand has seven pairs. It is one of the two exceptions of the "four melds and one pair" rule for winning hands, the other being kokushi musou. Because the hand does not use melds, it can only be closed.
Under most rulesets, no two pairs may be identical (certain house rules may allow duplicate pairs, though).
Tile diagram
Winning tile:
Development
Tenpai for chiitoitsu always uses the wait of tanki (pair wait) in order to complete the seventh and last pair for the hand.
Note that the pairs must be distinct; having four of the same tile does not count as two pairs under standard rulesets. Even in rules that do allow four-of-a-kind to count as two pairs, a call for "kan" would not count, as a kan is treated as a triplet.
Hand interpretation
Unlike most mahjong hands, chiitoitsu is an exception to the "four groups and a pair" pattern. Instead, tiles are groups into pairs or toitsu. As such, the tile groupings cannot be interpreted other ways. For this reason, chiitoitsu is granted a unique fu count of 25 (which is not rounded).
Shanten
The shanten count for chiitoitsu is simpler to count, which can be marked by the number of pairs in the hand.
| Shanten | Pair count | Hand | Comment |
|---|---|---|---|
| Tenpai | 6 |       |
Obvious choice for chiitoitsu while in tenpai or 1-shanten. The choice of riichi will depend on the waiting tile, current hand, and current score.
A 1-shanten hand waits to pair one of three tile types for tenpai. Upon reaching tenpai, one of the three must be discarded. |
| 1 | 5 |
| |
| 2 | 4 |  |
A hand with four pairs may consider chiitoitsu - only one more pair is needed to get to 1-shanten.
It can also go for the regular hand structure if the shapes are good to do so (e.g., a hand with many ryanmen + 1 sequence should go for the regular structure). Such a hand should still try and keep the option for chiitoitsu, though. |
| 3 | 3 |  |
A hand with three pairs is inefficient either way, unless a pair can easily be ponned. Prefer the regular hand structure, unless a 4th pair is drawn very early. |
| 4 | 2 |  |
Attempting chiitoitsu is unreasonable. It is better off using the regular hand structure. |
| 5 | 1 |
|
Vs Toitoi
Given the number of pairs in the hand, it may be tempting to pon in order to aim for toitoi. But, if you don't already have a triplet, chiitoisu is generally faster to complete. This is especially true if the hand is iishanten for chiitoitsu.
The decision for chiitoitsu/toitoi will depend on the point standings, the current round, the number of tiles available, and what the rest of the hand looks like. The following is a rough guideline on which to go for:
Chiitoitsu:
- Prefer chiitoitsu if a pair cannot be turned into a triplet (if both other copies of the tile are visible).
- Prefer chiitoitsu at 1-shanten (5 pairs).
- With 4 pairs + 1 other triplet, keep your options open, unless a pair cannot be turned into a triplet. The hand is currently 1-shanten for chiitoitsu, and can turn into a wider toitoi 1-shanten after a pon.
Toitoi:
- If you have 4 pairs and a tile group forms, tend to prefer the regular hand structure; this may or may not be toitoi.
- Exception: if the rest of the hand is isolated tiles or otherwise poor quality (e.g., 1244m2288p11s55s8s draw 2p), then prefer chiitoitsu, and/or keep the option for both chiitoitsu and the regular structure.
- Prefer toitoi when all of the pairs can be turned into triplets, and most/all of the pairs are easy to pon (honors/terminals).
- Prefer toitoi when the hand has another yaku, e.g., yakuhai or tanyao. This gives the option to go for a fast hand if a sequence forms, while still giving the chance for toitoi.
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 | |
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The composition of this yaku makes it very restrictive regarding its combination with other yaku. Chiitoitsu cannot be combined with any yaku dependent on tile groups of three, as this yaku consists of only pairs. Chiitoitsu combined with chanta gives honroutou, and it cannot be combined with junchan as there are only six different terminals, but chiitoitsu requires seven distinct pairs.
This yaku forbids kan, so rinshan is incompatible. Chankan is also incompatible; a hand in tenpai for chiitoitsu always has a copy of the winning tile, thus making it impossible for other players to make the added kan call required for chankan.
With iipeikou or ryanpeikou
A chiitoitsu hand may collect sequential series of paired tiles, which may look like iipeikou or even ryanpeikou. Both yaku are incompatible with chiitoisu, as once again, all tiles are considered to be in pairs, not sequences.
Value
As a special exception to scoring, this hand is always given 25 fu. No other fu are awarded: not for yakuhai pairs, tanki waits, or closed ron. It is not rounded up to 30 fu. This produces a distinct set of scoring values:
| Position | 2 han | 3 han | 4 han | 5 han or more |
|---|---|---|---|---|
| Non-dealer tsumo Non-dealer ron |
Not possible 1600 |
800/1600 3200 |
1600/3200 6400 |
Mangan, Haneman, etc. |
| Dealer tsumo Dealer ron |
Not possible 2400 |
1600 4800 |
3200 9600 |
A 2 han chiitoitsu tsumo is not possible, as chiitoitsu is always closed, so it also scores mentsumo. Like all hands, once you reach 5 han or more, fu is no longer relevant for scoring.
Note that, if the hand is below mangan, chiitoitsu can be thought of as a 1 han 50 fu hand.
- 2 han 25 fu = 1 han 50 fu
- 3 han 25 fu = 2 han 50 fu
- 4 han 25 fu = 3 han 50 fu
High scoring chiitoitsu hands are possible even without dora. The highest possible hand is riichi, ippatsu, tsumo, 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 for an additional 1 han. In some rule variations, this hand is an optional yakuman, known as "daisharin", "daichikurin", or "daisuurin", depending on the suit.
With dora
All tiles in this yaku must be in pairs. Therefore the dora tiles also tend to occur in pairs. The red dora, if used, are exceptions, since they can be paired with non-red versions of the tile.
External links
- Chiitoitsu in Japanese Wikipedia
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