Koi Koi – frequently called “Come On” by American players – is similar to Matching Flowers except it utilizes a few different dekiyakus and only allows for two active players per hand. While as many as five players may sit at the Koi Koi table, once two have elected to play the remaining players are forced to drop out. If a player that would normally be forced to drop out really wants to play their hand, then they may pay a penalty point to another player to take their place in that round. Because Koi Koi accommodates so few players, each participant is initially dealt eight cards with an additional eight cards dealt face up on the board.
Koi Koi is a game of calculated risks. Because the key to winning is creating the largest combinations, players must decide if they will accept a smaller combination or test their luck by waiting for a larger one. If a player has a made combination but chooses to wait for a larger one, then they challenge their opponent by announcing “koi koi” or “come on.” If their opponent makes a combination before they do, then the challenger loses all points from that hand, but if the challenger achieves a second or larger combination first, then they not only win, but they may double the value of that combination. Players may elect to continue this challenge into third and fourth combinations, thereby tripling or even quadrupling their points.
To make Koi Koi more challenging, individual card values are not counted – players can only earn points by creating a dekiyaku. The approved Koi Koi combinations and their point values are as follows:
Five Brights – 5 points
Four Brights – 5 points
Blue Tanzaku (three cards) – 5 points
Red Tanzaku (three cards) – 5 points
Any Five Tanzaku – 1 point
Any Five 10-point Cards – 1 point
Any Ten 1-point Cards – 1 point
Additionally, for dekiyakus that allow for “any” combination of qualifying cards, if a player adds another card that fits within that category then they may also add another point. For example, if a player with Five Tanzaku picks up another tanzaku, then they may add an additional point.
