Kuikae

Kuikae 「喰い替え」 is a particular restriction applied to tile calls, especially involving chii. It is commonly referred to as "swap calling". Generally speaking, when swap calling is forbidden, when a player calls another player's discard, the following discard cannot be another copy of the tile they just called, nor can it be another tile that also completes the chii that the player just called for.

Examples

Example 1: Different end tile of a chii

Player has in hand:
Left player discards:
Chii is called to form
is left over, but cannot be discarded on the same turn, because it completed the on the other end.

Example 2: Middle tile of a chii

Player has in hand:
Left player discards:
Chii is called to form
is left over, but cannot be discarded on the same turn, because it is another copy of the tile that was just called.

Example 3: Same end tile of a chii

Player has in hand:
Left player discards
Chii is called to form
is left over, but cannot be discarded on the same turn, because it is another copy of the tile that was just called.

Example 4: Pon

Any player discards:
Pon is called to form (orientation depending on tile source)
is left over, but cannot be discarded on the same turn, because it is another copy of the tile that was just called.