Ryuuiisou

Conditions

• Every tile in the hand must be one of the “green” tiles: 2s, 3s, 4s, 6s, 8s (bamboo) and/or 6z (hatsu/green dragon)
• No other tiles are allowed — not even other bamboo tiles like 1s, 5s, 7s, or 9s
• The hand can be open — calling pon or chi on green tiles is allowed
• The only possible sequence is 2-3-4 of bamboo; all other melds must be triplets
• Hatsu (green dragon) is not required in all rulesets, but some rulesets do require at least one hatsu tile to be present

Strategy Tips

• Ryuuiisou is named “all green” because the qualifying tiles are depicted with only green ink on traditional bamboo tiles. The valid tiles are a quirky set to memorize: 2, 3, 4, 6, 8 of bamboo plus hatsu.
• The 2-3-4 bamboo sequence is the only possible sequence in ryuuiisou, which severely limits your hand structure. Most ryuuiisou hands rely heavily on triplets of 2s, 3s, 4s, 6s, 8s, and hatsu.
• If your starting hand has several green bamboo tiles plus hatsu, keep ryuuiisou in mind as a long-shot possibility. Even if you don’t achieve the yakuman, you may be building toward honitsu or chinitsu with bamboo tiles, which gives you a fallback plan.