Kuikae

Kuikae 「喰い替え」, commonly referred as "swap calling", is a rule on discards after making a tile call.

If kuikae is disabled ("kuikae nashi"):

• When a player calls another player's discard, the following discard cannot be another copy of the just-called tile.
• When a player calls chii, the following discard cannot be a tile that could complete the just-called chii.
• If, after calling, every possible discard would violate the above rules, the call is not allowed.

Kuikae nashi is the more common rule used today.

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. Player has in hand:
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.

Example 5

1. After calling three times, player has in hand:
2. Left player discards:
3. If chii is called to form , then only and are left over.
4. However, discarding either or will violate the rules above. Therefore, player cannot call chii on .

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, because the discarded tile would've completed the mentsu used in the call. This allows players to make calls that do not advance their hand, but achieve other goals.

When kuikae is allowed, players can:

• Call tiles in order to "easily" disrupt others. Players can make otherwise meaningless calls in order to interrupt other players' ippatsu or shift the haitei draw.
• Call tiles in order to "easily" skip having to draw a (potentially dangerous) tile late in the round. This is especially important if in tenpai, due to the noten penalty.
  • For example, suppose a player had a yakuless tenpai, an opponent has declared riichi, and there are 3 tiles left in the wall after the right opponent's draw. If the player had a 345-sou sequence in hand, and the right opponent discards a 3-sou, it is possible to chii the 3-sou and discard 3-sou. This kuikae call essentially skips the player's turn, allowing tenpai to be retained without the chance of dealing in.
• Call tiles in order to "easily" raise the value of their hand. Kuikae can be used to change the end of a sequence (as shown in Example 1) to obtain yaku, such as tanyao or sanshoku. It can also be used to obtain dora, such as calling a red five, then discarding a five afterwards.

By restricting kuikae, these cases become less prevalent: it is harder to disrupt players for the sake of disruption, and it is harder to gain value with an otherwise useless call. Allowing kuikae is not an inherently bad thing - these disruptive tactics have a strategy of their own. However, since kuikae nashi was the more popular rule, more and more places started to use it. Today, kuikae nashi is the standard rule, and most rulesets include some form of it.

Even in a kuikae nashi ruleset, it is possible to call tiles to disrupt others or gain value (though, as mentioned, it is harder to do so).

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: (or )
3. Chii is called to form (or )
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.

Penalty

In real play with kuikae disabled, if a player makes a kuikae call, the hand will be declared dead.

In online play, such situation cannot occur because the software will handle the situation.

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, players 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 former 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, pl;ayers 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?