Ankan, daiminkan, and kakan
A kan (カン) is a meld of four identical tiles, the third type of call after pon and chii. It comes in three forms: the closed ankan, built entirely from tiles in hand; the open daiminkan, which claims a discard to complete the four; and the added kakan (shouminkan), which extends an existing pon with the fourth tile drawn later.
What happens after declaring kan
Declaring a kan triggers three effects: you draw a replacement tile (rinshan) from the dead wall, the live wall shrinks by one tile, and a new kan-dora indicator becomes active. Under Tenhou rules, it appears immediately for ankan and normally after the following discard for daiminkan or shouminkan. WRC 2025 reveals it before the discard for all three types. Winning on the replacement tile scores rinshan kaihou.
Fu, chankan, and kan after riichi
Kan adds fu and reveals dora that helps everyone. A shouminkan can be robbed by chankan; under both Tenhou and WRC 2025, an ankan cannot be robbed, even by kokushi musou. After riichi, Tenhou only permits an ankan with the tile just drawn that preserves the same waits, even if structure or yaku change. WRC also requires the same structure. Four kan in one hand form suukantsu.