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Genbutsu
Genbutsu is a tile already sitting in an opponent's river: furiten makes it safe against that player's ron, not against the other players.
The principle
Genbutsu (現物, "the real thing") is any tile that already appears in an opponent's river (kawa). The furiten rule forbids a player from winning by ron on a tile they have themselves discarded. A tile in an opponent's kawa is therefore safe against that player's ron.
Rule and example
Genbutsu is not limited to an opponent's own discards. Against a riichi, any tile discarded by anyone after the declaration, and which the riichi player let pass without calling ron, is also safe against that player's ron. Passing on a winning tile while in riichi locks the player into furiten for the rest of the hand, not just until the next draw.
What changes
Against one specific player, genbutsu is a direct certainty against their ron. It does not protect against the other two players or against tsumo. Complete public constraints can sometimes exclude every remaining shape, but counting only the other copies of the tile is not always enough: a run or special shape can wait on it without already holding a copy. Suji, partial kabe and one-chance remain probabilistic.
Mistake to avoid
Common pitfall: genbutsu is per-opponent. A tile safe against the riichi player can still deal into another player's concealed hand. Against several threats, look for tiles safe against everyone at once, and remember that the opponent's river is your treasure map.
Rules references
- Tenhou rulesReference profile used for game mechanics and scoring.
- WRC Rules 2025International rules compared whenever their options differ from Tenhou.