Japanese Mahjong, especially called Riichi Mahjong (リーチ・マージャン）, is a very specific remake from Japan of the traditional Chinese Mahjong. It is as close and yet far from Chinese Mahjong as Shôgi (Japanese Chess) can be the same and yet different from original Chess.
What Is It about?
Mahjong was brought to Japan in 1904, but the Riichi form that is used in modern times probably originated from the 1920s. Today, the worldwide famous Mahjong Association officially recognized the complete rules of Riichi Mahjong for Tournaments.
The main differences are :
1) The 1-Yaku minimum: In order to win a hand, it can only be validated when your hand has at least one of the Yaku (specific hand combinations) in it.
2) Dora: A specific bonus tiles are indicated by the flipped tile from the dead wall and providing other possible Han bonus.
3) Riichi: When a player is Tenpai (one tile away from having a Mahjong hand, valid or not), he can bet a 1000 points chip to add one Yaku to his hand (thus validating a possible invalid hand). Winning with a Riichi hand allows access to the hidden ura-dora, which is an added dora indicator located underneath the revealed dora tile.
4) Abortive draws: Specific conditions, which ends a hand without winning prior to the drawing of all tiles, aside from the dead wall.
5) Scoring system: Much more complex than in Chinese Mahjong, it is based on hand combinations (Yaku) providing multipliers (Han) that combine with some other circumstantial points like the type of tiles in the hand (Fu) for any 4 han or less. The combination of Han and Fu correspond to a chart (and even an equation) to finally produce the hand’s scoring points (Ten).
Some other minor elements in the Riichi Mahjong differ from the original Mahjong but are not important enough to be fully mentioned, like the Red 5 tiles (a non-official variant sometimes used which gives bonus like the Dora) or the validation of some Yaku (when the hand must be kept hidden or not, depending on the Japanese region where the game is played).
How To Play
At the start of the game, all tiles are shuffled and placed in rows (called “walls”) face-down on the table (see Setting Up below, if playing with physical tiles). Once starting hands have been dealt, the dealer takes a tile from the end of the wall. He then either wins from this tile, or discards a tile of their choosing, placing the discarded tile in front of them. Discards are placed in rows in front of each player, in chronological order, and typically in rows six tiles long.
When a player discards a tile, other players may call it if they wish to use it to complete a set. A tile can only be picked up if it is the final tile in a complete set, which must be displayed face up to the side of the player’s remaining hand. Once a set is called (melded), it no longer forms an active part of the players hand and the tiles that form that meld may not be discarded or swapped. If the tile is not called, then play goes anti-clockwise, and the player to the dealer’s right then picks up a tile from the end of the wall, and will then either discard or complete their hand to win. If the tile is called, the turn switches to the player who called, and play resumes from their position, skipping any players who would otherwise have had a turn.
Play continues until either a player wins, or all tiles in the wall are dealt (except for the dead wall – the last 14 tiles in the wall), in which case the hand is drawn. If the dealer wins, or is in tenpai (one tile away from winning – a 14th tile will complete their hand) in the case of a draw, then they retain their dealership, else dealership passes to the player on their right. The first round is East round, and once all players have been dealer once (i.e. the dealer is the person who started the game as dealer initially) the game becomes South round. Typically a game will consist of an East and a South round.