Ooyamaneko.net

• The most recent discard can be claimed by any of the other players, provided they can complete a winning hand, a kōtsu, or a kantsu. A claimed kōtsu or kantsu may result in players losing their turn, as play continues from the claiming player, not from the discarding player.
• The player about to begin his turn can claim the most recent discard for a shuntsu. If the player doesn’t want to claim the discard, he begins his turn by picking the next tile from the wall.

When claiming a tile for a shuntsu, kōtsu or kantsu, the player first clearly calls “chii”, “pon” or “kan” respectively. Secondly, the player reveals the matching tiles from his hand. And thirdly, he discards a tile from his hand and takes the tile called for. For the third step the order of the two actions is not important: the player can take the claimed tile first and then discard, or the other way round.
Errors in the order above when claiming tiles should be pointed out to the player, but there will be no penalty.
The player should take the claimed tile before the next two players have made a discard. Failing to take the claimed tile in a timely manner results in a dead hand, since the player will have a false group.

Swap-calling (kuikae) is not allowed. It is forbidden to:
- Call a tile and immediately discard the same tile.
(E.g.: calling , melding , and discarding .)
- Call a tile for a shuntsu and immediately discard the tile from the other side of the shuntsu.
(E.g.: calling , melding , and discarding .)

Claiming a tile to win takes precedence over any other claim. When several players declare a win on the same discarded tile, the player closer to the discarder, according to the turn order, takes precedence.
Claims for a kōtsu or kantsu take precedence over claims for shuntsu.

When it's not their turn, players have 3 seconds to claim a tile. If the most recent discard is claimed after the next player has picked a tile, but within three seconds after the discard, the picked tile is replaced in the wall.
During their turn, players are not limited in time to play, but repeatedly taking an overlong time can be penalized for obstruction at the referee discretion.

By courtesy, East player is expected to wait until each player has sorted his hand before making his first discard.

A tile can only be claimed for a shuntsu from the player on the right of the discarder. Claiming the last discarded tile for a shuntsu is done by clearly saying “chii” and placing the tile face-up along with the two tiles from the hand that complete the group.

A player can make a shuntsu with only self-drawn tiles. He must not declare it.

Claiming the last discarded tile for a kōtsu is done by clearly saying “pon” and placing the tile face-up along with the two matching tiles from the hand.

A player can make a kōtsu with only self-drawn tiles. He must not declare it.

Claiming the last discarded tile for a melded kantsu is done by clearly saying “kan” and placing the tile face-up along with the three matching tiles from the hand. After revealing a new kan dora, the player takes a replacement tile from the dead wall and continues his turn as if he had drawn a tile from the wall. The dead wall always comprises 14 tiles, so after a kantsu is made the dead wall is replenished with the last tile of the live wall.

A melded kōtsu may be extended to a melded kantsu in a player’s turn after the player has taken a tile from the wall (as a normal draw or as a replacement tile), i.e. not in a turn where a tile was claimed for making a shuntsu or kōtsu. The player must say “kan” clearly, place the fourth tile by the rotated tile of the kōtsu, allow 3 seconds for other players' winning declarations, and then reveal a kan dora and take a replacement tile. The dead wall is replenished with the last tile of the live wall.

A concealed kantsu may be declared in a player’s turn after the player has taken a tile from the wall (as a normal draw or as a replacement tile), i.e. not in a turn where a tile was claimed for shuntsu or kōtsu. The player must say “kan” clearly, reveal the four tiles of the kantsu, then turn the two outside tiles face-down, reveal a kan dora and then take a replacement tile. The dead wall is replenished with the last tile of the live wall.
It's allowed to turn the two middle tiles face-down instead of the two outside tiles.
A player still has a concealed hand after declaring a concealed kantsu, if the player has no open groups.
A concealed kantsu cannot be robbed, except to win on the Thirteen Orphans yaku.

Note that four identical tiles only make a kantsu if they are declared as being a kantsu.

Only four kantsu can be declared by hand. When the fourth kantsu is made the game continues, but no further kantsu may be declared. Under no circumstance can a fifth kantsu be made.

Tiles in melded groups, as well as concealed kantsu, can not be rearranged to form other groups, and they can not be discarded.
After calling a tile, the relevant tiles from the hand are immediately exposed. It is allowed to make the discard before the claimed tile is taken. If the claimed tile is not taken within the next two opponents’ turns, i.e. before another two discards has been made, the player has a dead hand.
Melded groups and concealed kantsu are placed to the right of the players tiles in clear view for all players. Claimed tiles are rotated to indicate which player made the discard.
• If the tile was discarded by the player sitting on the left, the claimed tile is put on the left side of the group.
• If the tile was discarded by the player sitting in front, the claimed tile is put in the middle of the group.
• If the tile was discarded by the player sitting on the right, the claimed tile is put on the right side of the group.
A daiminkan (melded kantsu made by calling on a concealed kōtsu) has one rotated tile.
A shōminkan (melded kantsu made by promoting a melded kōtsu) has two rotated tiles: the extending tile is placed by the previously rotated tile.
A concealed kantsu hasn't rotated tiles; instead the two outside (or central) tiles are turned face-down.