Koi-Koi

The most widely played Hanafuda game. Two players compete over 12 rounds (one per month). Each round, players match cards from their hand to the table by suit, building a captured pile. When a player completes a scoring pattern (yaku), they choose: declare a win and collect points, or say ”Koi-Koi” (「こいこい」, “come on”) to continue playing for a higher score — at the cost of losing the bonus if the opponent scores first.

Setup

Shuffle the 48-card deck. Deal:

8 cards face-down to each player (hand)
8 cards face-up to the centre (field/table)
Remaining 24 cards face-down as the draw pile

The dealer (oya) plays first. If either player is dealt a Teshi or Kuttsuki (see below), they win the hand at once. If four cards of one month are dealt to the table, the deal is void and dealt again.

Turn Structure

Players alternate. On your turn:

Play from hand: choose one card from your hand and place it face-up.
- If it matches a field card by suit (month), take both and add to your capture pile.
- If two field cards match, you choose which to capture; if three match, you capture all three.
- If no match, the card remains in the field.
Draw from pile: flip the top card of the draw pile.
- Apply the same matching rules.
- If it matches a field card, capture it. If not, it stays in the field.
Check for yaku: if your captures now complete one or more yaku, you must choose:
- Declare win: the round ends; you score your yaku points.
- Say Koi-Koi: play continues. If you later complete additional yaku, your total score grows.

If you said Koi-Koi and the opponent completes a yaku before the round ends, the opponent scores double for that round.

A round also ends when both players have played out their hands. If nobody has stopped, the dealer scores one point and deals again (Oya-Ken, the dealer’s privilege).

Yaku (Scoring Patterns)

Bright Yaku

Yaku	Cards Required	Points
Goko ・五光 (Five Brights)	All 5 Brights	10
Shiko ・四光 (Four Brights)	Any 4 Brights, excluding Rain Man	8
Ame-Shiko ・雨四光 (Rainy Four Brights)	Any 4 Brights, including Rain Man	7
Sanko ・三光 (Three Brights)	Any 3 Brights, excluding Rain Man	5

Viewing Yaku

Yaku	Cards Required	Points
Tsukimi-de-Ippatsu ・月見で一杯 (Moon Viewing)	Full Moon (Aug) + Sake Cup (Sep)	5
Hanami-de-Ippatsu ・花見で一杯 (Blossom Viewing)	Cherry Curtain (Mar) + Sake Cup (Sep)	5

Note: Viewing yaku may be disabled by house rules in competitive play.

Animal Yaku

Yaku	Cards Required	Points
Ino-Shika-Cho ・猪鹿蝶 (Boar–Deer–Butterfly)	Boar (Jul) + Deer (Oct) + Butterflies (Jun)	5
Tane ・種 (Animals)	Any 5 Animals	1 (+1 per additional)

Ribbon Yaku

Yaku	Cards Required	Points
Akatan Aotan no Chofuku ・赤短・青短の重複	All 3 Red Poetry + all 3 Blue ribbons	10
Akatan ・赤短 (Red Poetry)	Pine + Plum + Cherry Poetry ribbons	5
Aotan ・青短 (Blue Ribbons)	Peony + Chrysanthemum + Maple ribbons	5
Tan ・短 (Ribbons)	Any 5 Ribbons	1 (+1 per additional)

Plain Yaku

Yaku	Cards Required	Points
Kasu ・カス (Plains)	Any 10 Plains	1 (+1 per additional)

The Sake Cup (Sep-Animal) counts as both an Animal and a Plain.

Dealt Yaku

Declared before play begins if dealt in the initial hand:

Yaku	Condition	Points
Teshi ・手四	Four cards of the same month dealt to one player	6 (or automatic win)
Kuttsuki ・くっつき	Four pairs (8 cards, 4 matched suits) dealt to one player	6 (or automatic win)

If a dealt yaku occurs, the round is redealt or scored immediately per house rules.

Scoring and Rounds

A standard game is 12 rounds, one for each month, though players may agree on fewer. The first dealer is the player who draws the earliest month; after that, the winner of each hand deals.

A hand worth 7 or more points scores double. If the opponent had called Koi-Koi, the winner’s score is doubled again, and the player who called scores nothing.

The highest total after the last round wins.

Attribution

Koi-Koi ・こいこい. Traditional Japanese card game. Rules checked against Wikipedia, Koi-Koi, which is the source for the doubling at seven points, Oya-Ken, the Sake Cup counting twice, the dealer, and the void deal.