Chiitoitsu

Chiitoitsu

Chiitoitsu (七対子, チートイツ) is a unique 2-han yaku where your entire 14-tile hand consists of seven different pairs instead of the standard four melds plus one pair structure. It’s one of the few yakus with an irregular hand pattern and always scores exactly 25 fu.

Detailed Explanation

Hand Structure

Unlike standard mahjong hands (four melds + one pair), chiitoitsu completely abandons the meld structure. You need seven distinct pairs—no triplets, no sequences, just pairs. For example:

• 2-2 bamboo, 4-4 bamboo, 6-6 dots, 8-8 characters, North-North, Green-Green, White-White

Each pair must be different tiles. You cannot have four identical tiles counting as two pairs—four of a kind is treated as a single entity and disqualifies the hand from chiitoitsu (though it could form a kan in a standard hand).

Requirements and Restrictions

Closed Hand Only: Chiitoitsu cannot be called open. No pon, no chi, no kan. You must draw all 14 tiles yourself.

Seven Different Pairs: The seven pairs must use different tile types. Four 3-bamboo tiles don’t count as two pairs for chiitoitsu purposes.

Fixed Fu Value: Unlike other hands where fu is calculated from hand composition, chiitoitsu always scores exactly 25 fu. This simplifies scoring but caps the base value.

Strategic Considerations

Tile Acceptance: Chiitoitsu has excellent tile acceptance when building—any drawn tile that forms a pair brings you closer. This makes it forgiving in the early game when you’re unsure which direction your hand will take.

Dealer vs. Non-Dealer: Because of the fixed 25 fu, chiitoitsu scores:

• Non-dealer: 1,600 points (2 han, 25 fu)
• Dealer: 2,400 points (2 han, 25 fu)

These are modest scores, but chiitoitsu pairs well with other yaku (riichi, tanyao, honitsu) to push into higher scoring territories.

Dangerous Waits: Chiitoitsu typically has a tanki (pair) wait on the final tile, which is one of the weaker wait types. This can make winning difficult as you’re waiting for one specific tile rather than multiple acceptance tiles.

Compatibility with Other Yaku

Chiitoitsu is incompatible with toitoi (all triplets) since the hand structures are mutually exclusive. However, it stacks with:

• Riichi (1 han): Almost always combined
• Tanyao (1 han): If all pairs are simples
• Honitsu (3 han): If all pairs are one suit + honors
• Chinitsu (6 han): If all pairs are one suit

A chinitsu chiitoitsu hand (8 han total) is devastating when achieved.

Usage Example

Your starting hand has multiple pairs: 3-3 bamboo, 7-7 dots, East-East. You commit to chiitoitsu, discarding all unpaired tiles and hoping to draw more pairs. By mid-game, you have six pairs and need one more. You draw another 5-5 characters, completing seven pairs. You declare riichi (your only yaku besides chiitoitsu). When you win, you score 2 han (chiitoitsu) + 1 han (riichi) = 3 han at 25 fu, worth mangan (2,000 base points for non-dealer).

Related Terms

Toitoi: All triplets yaku. Structurally opposite of chiitoitsu but thematically related (both avoid sequences).

Pair: Two identical tiles. Chiitoitsu requires seven pairs.

Menzenchin: Closed hand requirement. Chiitoitsu must always be closed.

Fu: Minipoints in scoring calculation. Chiitoitsu uniquely has fixed 25 fu.