Kuikae

Kuikae 「喰い替え」, commonly referred as "swap calling", is a restriction to discards after making a tile call. When kuikae is disabled ("kuikae nashi"), 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 would also complete the chii that the player just called for.

Examples

Example 1: Different end tile of a chii

1. Player has in hand:
2. Left player discards:
3. Chii is called to form
4. 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

1. Player has in hand:
2. Left player discards:
3. Chii is called to form
4. 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

1. Player has in hand:
2. Left player discards
3. Chii is called to form
4. 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

1. 
2. Any player discards:
3. Pon is called to form (orientation depending on tile source)
4. is left over, but cannot be discarded on the same turn, because it is another copy of the tile that was just called.

Reasoning

The main purpose of tile calls is to push hands forward and reduce the number of shanten. However, a kuikae call doesn't reduce the number of shanten, as the tile to discard can make a group with the tiles used for calling to form a mentsu. This kind of behaviour is usually not recognized to be "meaningful" to the calling player, but to disturb other players, e.g. utilizing kuikae on purpose to eliminate ippatsu or haitei. Without kuikae, it is still possible to make disruptive calls, but it becomes harder.

Note that kuikae is not always meaningless to the player himself/herself. The use of kuikae often includes:

1. Skipping a chance to draw to prevent drawing a dangerous tile near the end of a round, especially when in tenpai, due to the noten penalty.
2. Changing the end of a shuntsu (as shown in Example 1) to obtain yaku, especially tanyao, sanshoku, chanta, ittsu, etc.

While allowing kuikae is not inherently bad, more and more people preferred playing with kuikae disabled, so the kuikae rule became popular today.

Circumventing Kuikae

With certain complex tile shapes, it is possible to make kuikae-like tile calls without violating the kuikae rule. For example:

1. Player has in hand:
2. Left player discards
3. Chii is called to form
4. are left over.
   1. cannot be discarded on the same turn due to kuikae; however,
   2. is not connected to , and can be discarded immediately.

If was the only yaochuuhai in the hand, the hand now acquires tanyao. This would not have been possible if the player called chii with to form , in which case discarding would be forbidden by kuikae.

Rule Variations

Main article: Rule_variations#Kuikae

Many, if not most, rulesets disallow kuikae. There are a few variations to the rule, though:

• Generally, when kuikae is not allowed, you are unable to discard the exact tile drawn, and when calling chii, are unable to discard any tile that would complete said chii.
• Some rulesets (such as JPML A) may disallow discarding the exact tile that was called, but allow any other discard. For example, under this rule, with a sequence of 123, you can call chii on 4, discard 1, and have a 234 set.

External links

• 喰い替え

Kuikae in Japanese Wikipedia

• Why to use Kuikae rule in Riichi Mahjong?