Curriculum · 36 / 50
Defense: recap
Recap of the Defense chapter: furiten and genbutsu, suji, walls (kabe), and choosing between folding (betaori) and pushing against a riichi.
The principle
Defense rests first on furiten: a player in tenpai can never ron a tile already sitting in their own kawa. Every tile a riichi opponent has discarded is therefore genbutsu and safe against their ron. Tiles discarded by others after riichi and passed without ron become safe against that ron too, because passing a winning tile after riichi locks the player into furiten for the rest of the hand.
Rule and example
Beyond genbutsu, suji gives partial safety. If the riichi player discarded a 4, a ryanmen waiting on the 1 (a 2-3 shape) or on the 7 (a 5-6 shape) would leave him furiten on that 4, so the 1 and the 7 are suji, safer against a two-sided wait. Be careful: suji only guards against ryanmen, since a tanki, shanpon, or kanchan wait can still catch a suji tile.
What changes
Walls round out the read. Four visible copies make certain sequences impossible. With three visible copies, one-chance still leaves one possible copy and does not make a tile safe. Kabe never protects against every tanki or shanpon shape.
Mistake to avoid
The push or fold choice depends on hand value and distance, wait quality, safe tiles, turn, score and estimated threat. No riichi guarantees mangan, and no simple rule replaces that contextual comparison.
Rules references
- Tenhou rulesReference profile used for game mechanics and scoring.
- WRC Rules 2025International rules compared whenever their options differ from Tenhou.