About This Game

Experience Koi-Koi, the most popular rule set of the traditional Japanese card game Hanafuda, reimagined as a fast-paced, strategic two-player battle.

Even if you’ve never played Hanafuda before, this game is designed to guide you naturally through your first match.

Highlighted card options, automatic capture suggestions, and intuitive visual cues ensure you always understand what you can do—and how close you are to completing a powerful yaku (scoring hand).

With a single button, you can check the full list of hands at any time.

Enjoy the depth of Hanafuda with the smoothest, most accessible experience possible.

🎴Differences Between the Full Version and the Demo

In addition to everything included in the demo, the full version includes:

• Always-available Online Multiplayer

• Watch Mode (spectate AI vs. AI matches)

• Hard Mode (Challenge a stronger AI)

• No-Sake Mode (CPU matches with the Sake Cup card disabled)

• Steam Achievements (including unlocks for specific winning hands)

• Steam Leaderboards (view top players’ match results)

• Steam Cloud Saves

• Support for mouse and Steam Deck touch input

• Music Room

🎴Planned Features for Early Access

In the current Early Access version, we’re considering the following features for future updates:

• Story Mode / Arcade Mode, aiming for an ending *Current scope

Note: Plans may change based on development progress and community feedback.

🎴 Online Multiplayer

• Quick Match
  Match with a random opponent online.

• Friends Match
  Match online with players on your Steam Friends list.

• Create Private Room
  Create a private room using a custom ID and invite other players to join.
  (Share the room ID via chat or other means.)

• Join Private Room
  Join an existing room by entering its ID.

• Log
  View the results of your last 12 online matches and check your opponents’ Steam profiles.

A Private Room ID is created by choosing any 6-character code.

During online matches, to maintain a fast-paced experience, the pause function and hand list are disabled, and all inputs are subject to a time limit.

🎴Watch Mode (Spectate AI vs. AI Matches)

In Watch Mode, you can spectate AI vs. AI matches between Normal and Hard.

You can also check the most recent match log by selecting “Browse Local Files” in Steam, then opening `watch.log` under the `save` directory.

`watch.log` includes various metrics showing why the Hard AI chose each move.

It might be fun to have a generative AI analyze `watch.log`.

Note: The Hard AI is still being tuned and improved (we plan to keep updating it throughout Early Access). Please feel free to share your feedback and findings with the community.

🎴Music Room

In this game, the soundtrack is implemented using the YM2612 (OPN2) sound chip built into VGS-X. You can preview the music with a piano-style keyboard display from the Music Room.

🎴 Features

• Faithfully follows the official “Koi-Koi” rules used in tournaments and by Nintendo

• All cards show their month (1–12) and point value (20 / 10 / 5 / 1) in Arabic numerals

• Designed so even beginners can quickly understand the gameplay

• Strategic and thrilling matches with risk-reward “Koi-Koi” doubling mechanics

🎴 What is Hanafuda?

Hanafuda (花札) is a traditional Japanese playing card game derived from naipes, a type of card introduced from Portugal in the 1540s.

The deck consists of 12 suits representing the months from January to December, for a total of 48 cards.

Each month has four cards, divided into the following four categories:

• Bright (Hikari-fuda) — 20 points, 5 cards in total. The highest-scoring cards.

• Animal (Tane-fuda) — 10 points, 9 cards showing animals or objects.

• Ribbon (Tanzaku-fuda) — 5 points, 10 cards featuring poetic ribbons.

• Chaff (Kasu-fuda) — 1 point, 24 cards showing small background motifs.

Among the Ribbon cards:

• Those from January, February, and March are called Red Ribbons (Aka-tan) — red ribbons with writing.

• Those from June, September, and October are called Blue Ribbons (Ao-tan) — blue ribbons without text.

Hanafuda is also known as Hana-karuta or Hana-koppai (literally “flower cards”).

Interestingly, Nintendo, originally founded in 1889 as Nintendo Koppai, began as a Hanafuda card manufacturer —

a fascinating piece of history showing how deeply these traditional cards are woven into Japanese culture.

🎴 What is Koi-Koi?

Koi-Koi is a two-player duel that blends elements of poker and mahjong.

The game begins with 8 face-up table cards, 8 cards dealt to each player,

and a remaining deck of 24 cards.

Players (dealer and opponent) take turns playing one card from their hand.

If it matches the same month as a card on the table, both cards are captured.

If not, the played card is discarded onto the table.

Then, the player flips the top card of the deck and captures or discards it in the same way.

These steps are repeated alternately until both players run out of cards.

When a scoring hand is completed with captured cards, the player may choose either to “Finish” (end the round) or declare “Koi-Koi” to continue.

If you declare Koi-Koi and your opponent completes a scoring hand afterward, the round immediately ends: your opponent’s score is doubled, and your score for the round becomes zero.

If your completed hand is worth 7 points or more, your score for the round is doubled.

Furthermore, if your opponent has declared Koi-Koi and you win with a 7-point (or higher) hand, the score is quadrupled.

Official matches consist of 12 rounds, and the player with the higher total wins.

In this game, you can also choose from four match-length modes:

• Very Short (2 rounds)

• Short (4 rounds)

• Half (6 rounds)

• Full (12 rounds)

Koi-Koi offers deeper strategy than poker while remaining much simpler than mahjong — making it a balanced game that sits comfortably between the two.

There is naturally some correlation between strategic depth and rule complexity.  

Koi-Koi is slightly more intricate than poker, but that added complexity createsa rewarding layer of decision-making that greatly affects the outcome of each round.

For example, if you declare Koi-Koi while holding five Animal cards (Tane), and later capture a sixth, this counts as completing an additional scoring hand.

After a new hand is completed during Koi-Koi, you are required to end the round immediately.

Rules like this add nuance to the game while giving skilled players more room to outthink their opponent.

To keep the experience approachable, this game streamlines such detailed rules through clear visual guidance and controlled flow, making Koi-Koi intuitive even for newcomers while preserving its strategic depth.

🎴 List of Hands (12 Official Roles)

Press Y (or △ / S key on keyboard) during play to check the full list of hands anytime.

Cards you have already captured are highlighted in the list,

making it easy for beginners to see which cards they still need to complete a hand.

1. Gokō (Five Brights) — 10 pts

• All five Bright cards.

• Cancels Shikō and Sankō.

2. Shikō (Four Brights) — 7 or 8 pts

• Four Brights.

• 7 pts if includes Willow (November), otherwise 8 pts.

• Cancels Sankō.

3. Sankō (Three Brights) — 5 pts

• Three Brights excluding Willow (November).

4. Hanami de Ippai (Cherry Blossom Viewing with Sake) — 5 pts

• March Bright (cherry blossom) + September Animal (sake cup).

5. Tsukimi de Ippai (Moon Viewing with Sake) — 5 pts

• August Bright (moon) + September Animal (sake cup).

6. Inoshikachō (Boar-Deer-Butterfly) — 5 pts + bonus

• June, July, and October Animals.

• +1 pt for each extra Animal (max 12).

• Cancels “Animal Set”.

7. Animal Set — 1 pt + bonus

• 5 or more Animal cards.

• +1 pt for each additional. (e.g., 7 Animals = 3 pts)

8. Red & Blue Combo — 10 pts + bonus

• All three Red Ribbons + all three Blue Ribbons.

• +1 pt per extra Ribbon (max 13).

• Cancels Red, Blue, and Ribbon Set hands.

9. Red Ribbons — 5 pts + bonus

• All three Red Ribbons.

• +1 pt per extra Ribbon.

• Cancels “Ribbon Set”.

10. Blue Ribbons — 5 pts + bonus

• All three Blue Ribbons.

• +1 pt per extra Ribbon.

• Cancels “Ribbon Set”.

11. Ribbon Set — 1 pt + bonus

• 5 or more Ribbon cards.

• +1 pt per additional.

12. Plain Set — 1 pt + bonus

• 10 or more Chaff cards.

• +1 pt per additional.

• Note: The Sake Cup (September Animal) also counts as Chaff.

🎴 Controls

• A / × / Z key — Play a card / Confirm

• B / ○ / X key — Cancel / Go back

• X / □ / A key — Fast-forward animations

• Y / △ / S key — Show hand list

• Menu / Options / SPACE key — Pause the game

• Ctrl + R key — Reset Program

• Ctrl + Q key — Exit Program

🎴 Recommended For

• Beginners who’ve always wanted to try Hanafuda

• Players looking for a quick, two-player battle game

• Fans of Japanese-style, strategy, and mind-game experiences

• People who enjoy tabletop games like poker or mahjong

🎴 Content Usage Policy (Streaming & Media)

You are free to create and publish content using this game (including gameplay videos, live streams, articles, and social media posts) without obtaining prior permission.

This applies to both commercial and non-commercial use, including monetized content.

However, redistribution or reuse of in-game assets (such as graphics, audio, or music files) as standalone materials is not permitted.