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

If either player is dealt a dealt yaku (Teshi or Kuttsuki, see below), they may declare it immediately for an automatic win.

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 exhaust their hands and the draw pile. If neither player declared a win, the round is a draw (no points scored).

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 in some house rules.

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. The player who dealt first in round 1 switches each round, or the previous round’s winner deals.

If you declared Koi-Koi and won the round, your score is doubled.

If you said Koi-Koi and the opponent wins the round, the opponent’s score is doubled.

A target score (e.g. 50 or 100 points over 12 rounds) determines the match winner, or simply the highest total after 12 rounds.

Attribution

Koi-Koi ・こいこい. Traditional Japanese card game. Rules in the public domain. Primary source: Wikipedia (Koi-Koi); secondary: Pagat.com (Hanafuda).