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The object of the game is to form special card combinations called "yaku" (or sets) from cards accumulated in a point pile. Players can gain cards in their point piles by matching cards in their hands, or drawn from the draw pile, with cards on the table. Once a yaku has been made, a player can stop to cash in points, or keep going (referred to as "koi-koi", hence the name of the game) to form additional yaku for more points. The point values assigned to individual cards have no effect on the score, but they are helpful to judge their value in forming yaku.
An initial dealer (called the "oya", or "parent"), is decided upon when the game starts. This can be done with any method (rock-paper-scissors, dice roll) the players agree upon. A hanafuda-specific method involves random card draw: each player draws a single card; the player who draws a card from the earliest month is the oya. If both players draw a card from the same month, the player with the higher value card becomes the oya. The other player is called the "ko".
To deal, the oya deals eight cards to the ko (face down), then to the table (face up), and then to themselves (face down), though this is normally done with two or four cards at a time. The rest of the cards are set aside as a draw pile, and then the game begins starting with the oya.
On a player's turn, they may match by suit (that is, by month/flower) any one card in their hand with one on the table and take both into their point pile. If they cannot match a card from their hand, they must discard a card face up to the table. After matching or discarding a card, they then draw one card from the draw pile and place it face up on the playing area. If this card matches any card now on the table, they must match that card and take both for their point pile; otherwise, it becomes part of the table. If the played card matches two cards on the table, the player gets the choice as to which card to match and therefore keep in addition to the played card. In the event that three cards of a same suit are on the table and a player plays the fourth one, they collect all cards of that suit and take them into their point pile.
After a player's turn ends, if they made at least one yaku that turn, that player must then make a choice. They may end the hand and add the value of their yaku to their point total, or they can choose to continue playing (calling "koi-koi") in an effort to gain more points. In some versions, a player may only call koi-koi once per hand; in others, a player may call koi-koi on multiple yaku-forming turns. Calling koi-koi leaves the player vulnerable, as if their opponent is able to form a yaku before the caller forms another, the opponent gains double their score and the caller earns nothing. If a player has yaku totaling 7 or more points when the hand ends, that player earns twice that value. If a player hits 7 or more points and their opponent had called koi-koi, he gets both doubling bonuses for a total of four times their score.
The player who won the last hand becomes the new oya, and a new hand is dealt. Should both players ever run out of cards to play without having formed a yaku on the last play, the oya gains one point, and the next hand begins with the same oya (this is called Oya-Ken, meaning "Dealer's Privilege"). Generally, play continues for 12 hands, with each hand representing a month in the year, but the players can decide to play for a different number of rounds before the game starts.
Some groups, when gambling, will require the player whose score was multiplied to pay a proportionately larger amount of the winnings (i.e. a player who continued play twice would pay twice as much as the other player, since their score would have been doubled).
The Sake Cup is unique in that, though technically classified as a 10-point card, it counts as both a 10-point card and a 1-point card at the same time. Some rules allow the Sake Cup to count as a 10-point card and two 1-point cards at the same time.
Additionally, November's 1-point card, the Lightning, is sometimes used as a wild card that can match any card in some games.
If certain combinations of cards are won during play, extra points apply. Sometimes, players will be paired across the table when this rule is used (in multi-player Koi-Koi) to increase the chance of getting combos. Below is a list of special combinations with example point values. Different rulesets give different point values and some do not include the tsukimi-zake and hanami-zake yaku.
Some yaku can be considered extensions of others. For example, one may qualify for both Akatan and Tanzaku by having the Akatan combination as well as two additional five-point cards. In these cases, players are awarded points for both Akatan and Tanzaku (unless players decide only the single highest-scoring yaku counts).
|Points||Combo Name||Card Combo|
|6||Sankō (三光) "Three Brights"||Any three 20-point cards excluding the Rainman (Willow's 20-point card).|
|8||Shikō (四光) "Four Brights"||The four 20-point cards which exclude the Rainman (Willow's 20-point card).|
|7||Ame-Shikō (雨四光) "Rain Four Brights"||Any four 20-point cards including the Rainman (Willow's 20-point card).|
|15||Gokō (五光) "Five Brights"||All five 20-point cards.|
|5||Inoshikachō (猪鹿蝶) "Boar, Deer, Butterfly"||The Boar, the Deer, and the Butterfly (the 10-point cards from Clover, Maple, and Peony, respectively).|
|1||Tane (タネ) "Seeds"|
|5||Akatan (赤短) "Red Poetry Ribbons"||All 3 Red Poetry Ribbons (found in Pine, Ume, and Sakura).|
|5||Aotan (青短) "Blue Poetry Ribbons"||All 3 Purple/Blue Ribbons (found in Peony, Chrysanthemum, and Maple).|
|10||Akatan, Aotan no Chōfuku (赤短・青短の重複) "Duplication of Red and Blue Poetry Ribbons"||All 3 Red Poetry Ribbons and all 3 Purple/Blue Ribbons: the combination of Aka-tan and Ao-tan.|
|1||Tanzaku (短冊) "Poetry Ribbons"||Any five 5-point cards, which includes all Ribbons. One additional point is awarded for every additional 5-point card.|
|5||Tsukimi-zake (月見酒) "Moon Viewing, Sake"||The Moon and the Sake Cup (Pampas' 20-point card and Chrysanthemum's 10-point card). Cumulative with Hanami-zake.|
|5||Hanami-zake (花見酒) "Cherry Blossom Viewing, Sake"||The Sakura Curtain and the Sake Cup (Sakura's 20-point card and Chrysanthemum's 10-point card). Cumulative with Tsukimi-zake.|
|4||Tsukifuda (月札) "Monthly Cards"||All 4 cards of played hand month.|
|1||Kasu (カス) "Chaff"||Any ten 1-point cards, which are all normal (or literally, "chaff") cards. One additional point is awarded for every additional 1-point card.|
Instant wins and redeals
There are two special yaku such that, if a player is dealt them before play begins, they are immediately awarded points. Play then ends before it starts, and the game continues to the next hand. If either of these combinations are dealt to the table, however, the hand is declared void and a redeal occurs. These two combinations are as follows.
|Points||Combo Name||Card Combo|
|6||Teshi (手四)||Being dealt four cards of the same suit.|
|6||Kuttsuki (くっつき)||Being dealt four pairs of cards with matching suits.|
In popular culture
Koi-Koi is played a major role in the 2009 anime film Summer Wars. It is also one of the featured games in Clubhouse Games, as well as its successor Clubhouse Games: 51 Worldwide Classics. The game is often featured in the Yakuza series of video games as an included mini-games. The game is also played in Way of the Samurai 4(2011 video game), and Sakura Wars (2019 video game).
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- "歴史・遊びかた｜花札・株札｜任天堂". 任天堂ホームページ (in Japanese). Retrieved 2020-07-13.
- Provo, Frank (2006-10-13). "Clubhouse Games Review". Gamespot. Retrieved 2020-09-23.
- Vincent, Brittany (2020-07-10). "Clubhouse Games: 51 Worldwide Classics offers a perfectly punchy set of minigames". CNN Underscored. Retrieved 2020-07-13.
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