Riichi Mahjong · Yakuman

Ryuuiisou (All Green) in Riichi Mahjong: Yakuman Rules, Green Dragon or Not, Examples

In riichi mahjong, Ryuuiisou (all green) is a yakuman: all 14 tiles are ones printed entirely in green — 2, 3, 4, 6 and 8 bamboo and the green dragon. The 1, 5, 7 and 9 bamboo have red on them, so they don't count. Calls are allowed.

The rules for Ryuuiisou

• Only 2, 3, 4, 6, 8 bamboo and green dragon: six kinds, four copies each, just 24 tiles
• Pon, chi and kan are fine: still a yakuman when open
• Very few sets are possible: the only sequence is 2-3-4 bamboo; everything else is a triplet (2, 3, 4, 6, 8 bamboo, green dragon)
• No seven-pairs shape: there are only six green kinds, not seven

Ryuuiisou examples

The hands below are computed live by the same scoring code the game uses.

How it relates to other yaku

• Honitsu: ryuuiisou with the green dragon is always honitsu in shape; without it, chinitsu. A yakuman isn't added to regular yaku, though, so only ryuuiisou counts.
• Toitoi: with 2-3-4 bamboo the only sequence, ryuuiisou often takes the toitoi shape.
• Tsuuiisou, chinroutou: other yakuman built from a fixed set of tiles.

Ryuuiisou odds

Ryuuiisou practically never appears in this site's computer games, so here's the theory instead: only 24 of the 136 tiles are green (about 18%). The chance that 14 random tiles are all green — C(24,14) ÷ C(136,14) — is roughly one in two trillion, before even asking whether they form a winning hand. In real games it almost always grows out of a bamboo honitsu or chinitsu that happens to use only green tiles, plus a green dragon pon.

Ryuuiisou in other mahjong styles

• Chinese Official (Guobiao): "All Green", 88 fan (Guobiao fan list)

To try it yourself, open a table of free online riichi mahjong — yakuman are scored for you too.

FAQ

Is Ryuuiisou a yakuman?

Yes, ryuuiisou is a yakuman, open or closed.

Does Ryuuiisou need the green dragon?

Not in this game: 2, 3, 4, 6 and 8 bamboo alone also count, as on Tenhou and Mahjong Soul. Some rule sets require it.

Can you chi for Ryuuiisou?

Yes, but the only sequence you can make is 2-3-4 bamboo.

Related yaku

Honitsu Closed 3 / open 2 One suit plus honors — 3 han closed, 2 open. Examples, honitsu vs chinitsu, and how many tiles you need to go for it. Chinitsu Closed 6 / open 5 Every tile from one suit — 6 han closed, 5 open. Examples, chinitsu vs honitsu, and how many suited tiles you need. Tsuuiisou Yakuman All 14 tiles honors — a yakuman, called or closed, seven pairs allowed. Examples, combos and odds.