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Koi-Koi Rules

Detailed rules for Koi-Koi. Learn about game flow, koi-koi declarations, yaku list, and scoring.

Overview

What is Koi-Koi?

Koi-Koi is the most popular hanafuda game, played between basically 2 players (2 to 5 possible with the "enter/retire" system). The key excitement lies in the strategic decision of whether to declare "koi-koi" (continue) to pursue higher-scoring hands, or to declare "stop" to secure your current points.

Setup

Players2 (2-5 possible)
Hand8 each
Field8 cards
CardsAll 48

Game Flow

1

Play a Card from Hand

Play one card from your hand to the field. If there is a card from the same month, capture both cards and add them to your scoring pile. If no match, the card remains on the field.

2

Draw from the Pile

Flip the top card of the draw pile. If it matches a field card by month, capture both. If no match, the drawn card stays on the field.

3

Check for Yaku

After matching from the draw pile, check if your captured cards form any yaku (scoring combinations). If completed, choose "Koi-Koi" or "Stop". If not, the next player's turn begins.

4

Koi-Koi or Stop

Koi-Koi: Continue the game to aim for higher scores. However, if your opponent completes a yaku first, your previous yaku are nullified.
Stop: Lock in your current yaku score and end the round.

Hand Yaku and Redeals

Hand yaku are not used, but "teshi" (four of the same month in hand) or "kuttsuki" (three pairs of same-month cards) can be declared for a redeal.

Enter/Retire for 3+ Players

With 3 or more players, each player evaluates their hand and decides whether to participate. There is no retire fee or chase-out fee.

"Koi" and "Stop"

How Koi-Koi Works

This game does not use card point values. Players compete by forming yaku from captured cards.

When a player completes a yaku, they gain the right to choose whether to end the round or continue.

  • Declaring "Stop"

The completed yaku are finalized and the player collects the yaku score from the opponent. The round ends safely, but no further score increase is possible.

  • Declaring "Koi-Koi"

Neither yaku nor the result are finalized — the game continues. There remains a chance to increase the score.

After a koi-koi declaration, three situations may follow:

  1. You complete additional yaku — You gain the right to choose again. All your yaku remain valid, and declaring "Stop" now collects the total yaku score
  2. Your opponent completes a yaku — If they declare "Stop", all your previous yaku are nullified
  3. Neither side completes a yaku before hands run out — The round is a draw with no score exchange

What Counts as Additional Yaku

Not only completing a new yaku, but also gaining 1+ more cards in "count-based" yaku (Animals, Ribbons, Plains) counts as an additional yaku trigger.

Koi-Koi Multiplier

Score Calculation

Each koi-koi declaration doubles your final score.

Final Score = Total Yaku Points × 2^(Koi-Koi count)

  • 0 koi-koi (immediate stop): Base points
  • 1 koi-koi: ×2
  • 2 koi-koi: ×4
  • 3 koi-koi: ×8

Completed Yaku

Bright Yaku

Five Brights (Goko)

All 5 bright cards

15 mon

Four Brights (Shiko)

4 brights excl. Ono no Michikaze (Willow)

10 mon

Rainy Four Brights

4 brights incl. Ono no Michikaze (Willow)

8 mon

Three Brights (Sanko)

3 brights excl. Ono no Michikaze (Willow)

6 mon

Ribbon Yaku

Poetry Ribbons (Akatan)

3 red poetry ribbons (Pine, Plum, Cherry)

6 mon

Blue Ribbons (Aotan)

3 blue ribbons (Peony, Chrysanthemum, Maple)

6 mon

Animal Yaku

Boar-Deer-Butterfly

Butterfly (Peony) + Boar (Bush Clover) + Deer (Maple)

5 mon

Cherry Blossom Viewing

Cherry Curtain + Sake Cup

5 mon

Moon Viewing

Pampas Moon + Sake Cup

5 mon

Count-Based Yaku

Animals (Tane)

5+ animal cards

1+ mon

Ribbons (Tan)

5+ ribbon cards

1+ mon

Plains (Kasu)

10+ plain cards

1+ mon

Extra Points for Count-Based Yaku

Animals and Ribbons: 1 mon at 5 cards, +1 mon per additional card. Plains: 1 mon at 10 cards, +1 mon per additional card.

Sake Cup — Wild Card

The "Chrysanthemum Sake Cup" is originally an Animal card, but it can also be used as a Plain card (a card that "transforms" into a Plain). Furthermore, it can count for both categories simultaneously.

With the wild card rule adopted, the Sake Cup can potentially contribute to up to 4 yaku in a single hand (Moon Viewing, Cherry Blossom Viewing, Animals, Plains).

Determining the Winner

  • The player who declares "Stop" collects the total yaku score from the opponent
  • If neither player completes any yaku before hands run out, the round is a draw (no score exchange)
  • Each round constitutes one "month". The winner becomes the dealer for the next round. Play an agreed number of rounds (typically 12 rounds = one "year") to determine the final winner by total score