Ari-ari
By Kenji Tanaka · Updated
Definition
Ari-ari is the modern default rule set, named for the two things it allows (ari means yes): kuitan, the open tanyao, and atozuke, confirming your yaku on the winning tile itself. Most online clients run it. The strict opposite, nashi-nashi, forbids both and pushes the game toward slower closed hands. Which one is live changes what cheap open hands are even legal, so check before you call.
Ari-ari
Ari-ari (ありあり) is the most widely used rule set in modern riichi mahjong, characterized by permitting both kuitan (open tanyao) and atozuke (winning with an incomplete yaku). The term literally means “there is, there is,” referring to the presence of these two allowances.
Understanding Ari-ari
In riichi mahjong, players must form winning hands (agari) that contain at least one yaku (scoring pattern). However, different rule sets impose varying restrictions on which yaku are valid and under what conditions hands can be won.
Kuitan Allowance
Kuitan (喰い断) refers to forming tanyao (all simples) through an open meld rather than a concealed hand. In ari-ari rules, this is permitted. This means a player can win with tanyao even if one or more melds are open (called, from the discard). Under stricter rule sets (nashi-nashi), kuitan is forbidden, requiring tanyao to be formed entirely from concealed tiles.
The allowance of kuitan significantly impacts hand selection strategy, as players can pursue tanyao more flexibly by calling tiles from opponents’ discards rather than waiting for a fully concealed hand.
Atozuke Allowance
Atozuke (後付け, literally “attach afterward”) refers to completing a yaku only upon winning. In ari-ari rules, this is allowed. For example, a player might call tiles to form a hand that lacks a yaku at the moment of calling, but gains a yaku when the final winning tile is drawn or claimed. Common scenarios include:
- Drawing a tile that completes a yaku simultaneously with completing the hand structure
- Calling pon on a yakuhai pair with a shanpon wait, so the yaku only exists if you win on the honor tile
- Completing a yaku through the winning tile itself (such as forming a pair that completes a color sequence requirement)
In nashi-nashi rules, atozuke is forbidden; every yaku must be established before the winning tile is drawn.
Strategic Impact
The ari-ari rule set opens significantly more winning possibilities compared to nashi-nashi rules. Players have greater flexibility in hand development, can pursue open melds more aggressively, and have more opportunities to win with minimal yaku. This makes ari-ari more accessible to casual players while maintaining strategic depth.
The rule set encourages faster gameplay and more frequent winning hands, making it popular in casual clubs, online platforms, and tournament play worldwide.
Walking through Ari-ari
Consider a player with a hand containing 2-3-4 of bamboo (open meld), 5-6-7 of bamboo (open meld), 3-4-5 of dots (open meld), a pair of 5-characters, and 6-7 of characters waiting on 5 or 8 of characters. Upon winning, they score tanyao. This is valid under ari-ari rules because:
- Kuitan is allowed, so tanyao formed with open melds is valid
- Atozuke is allowed, so the yaku is established upon winning
Under nashi-nashi rules, this winning hand would be invalid.
Related Terms
Kuitan
喰い断
Kuitan is the rule that lets tanyao (all simples) score even after you open your hand with pon or chii. Where kuitan is allowed, calling tiles toward a cheap all-simples hand is a legitimate, fast route to a win. Where it is banned, tanyao must stay closed, and an opened simples hand can strand itself with no yaku at all. The rule splits table cultures: ari-ari rules, the default on the major online clients, allow kuitan, while stricter nashi-nashi rules forbid it and push the game toward slower closed hands. Check which rule is live before you call, because the entire logic of opening changes with it. With kuitan on, an early pon toward tanyao trades fair value for real speed; with it off, the same call can be a dead end.
Atozuke
後付け
Atozuke is winning with a yaku that only becomes valid on the winning tile itself, most often in an open hand shaped so that whichever tile completes the wait also supplies the yaku. Allowed under ari-ari rules, forbidden under nashi-nashi, where the yaku must be locked in before the final tile. The distinction decides whether certain borderline open waits are legal hands or dead ends.