Koi-Koi FAQ: Rules Questions and Playing Online

Question 1

What is Koi-Koi?

Accepted Answer

Koi-Koi (also written koi koi or koikoi) is a two-player game played with the 48 hanafuda, the Japanese flower cards. You capture cards by matching them with table cards of the same month and collect scoring sets called yaku. When you complete one, you either stop and score (Shōbu) or call “koi-koi” and play on for more, at the risk that your opponent scores first.

Question 2

What does “koi-koi” mean?

Accepted Answer

It comes from the call “koi!” (来い, “come on!”), which a player makes to keep the round going after forming a yaku; the game is named after it. It has nothing to do with koi carp (鯉) or love (恋), which only sound the same. Stopping to score is called Shōbu (勝負) or agari.

Question 3

Is Koi-Koi the same as hanafuda?

Accepted Answer

No. Hanafuda is the deck: 48 flower cards, four for each month of the year. Koi-Koi is one game played with it; others include Hana-awase and Hachi-hachi for three players, and in Korea Go-Stop is played with hwatu, the Korean form of these cards.

Question 4

Can three people play Koi-Koi?

Accepted Answer

Koi-Koi is a game for two, and this site plays it with two only. Some guides describe a three-player version with smaller hands, such as 7 cards each and 6 on the table. For three players, Nintendo describes Hana-awase and Hachi-hachi, and Korea’s Go-Stop, a close relative of Koi-Koi, is often played by three.

Question 5

How many cards are there, and how many are dealt?

Accepted Answer

A hanafuda deck has 48 cards: 12 months with 4 cards each. In Koi-Koi each player gets 8, 8 go face up on the table and the other 24 form the draw pile. At most 16 of them are turned over in a round, so at least 8 are never used.

Question 6

Which rules does this game use?

Accepted Answer

Koi-Koi has no single official rulebook; Nintendo’s published rules are often used as the reference. This game uses Nintendo’s yaku and point values, and the main differences are: both players play from a 25-point pool, doubling starts at 8 points instead of 7, every koi-koi call by either player raises one shared multiplier, Tane and Tan still count beside Inoshikachō, Akatan and Aotan, the Sake cup counts only as a tane, and the dealer stays after a drawn round. The house rules page lists every difference with Nintendo’s rule next to it.

Question 7

Do I have to capture when I can?

Accepted Answer

No. You may play any card from your hand, even one with no match while another card could capture; a card that does match must capture, though. Fuda Wiki describes the same freedom, while Board Game Arena and some English guides require a capture whenever one is possible.

Question 8

What if two or three table cards match my card?

Accepted Answer

With two, you choose which one to take. With three, your card takes all three, four cards at once. The card you turn over from the draw pile follows the same rules; here, a drawn card with a single option is taken for you after 5 seconds, while a choice between two always waits for you.

Question 9

When can I call Koi-Koi, and how many times?

Accepted Answer

At the end of your turn, when you have formed a yaku, or raised your total since your last call. In this game both players may call any number of times in a round, and each call raises the round’s multiplier by one; on the last turn, with both hands empty, only Shōbu is offered. Under Nintendo’s rules the round ends as soon as either player makes a yaku after a koi-koi.

Question 10

What happens if nobody makes a yaku?

Accepted Answer

If both hands run out before anyone calls Shōbu, the round is drawn and nobody scores; the same happens when someone called koi-koi and never improved. Here the same player deals the next round, while Nintendo passes the deal to the other player. Some tables give the dealer points instead (oya-ken, 親権).

Question 11

What are Teshi and Kuttsuki?

Accepted Answer

They are hand yaku, checked right after the deal: all four cards of one month in your hand (Teshi) or four pairs (Kuttsuki). Either scores 6 points and ends the round at once, as in Nintendo’s rules. If both players are dealt one, this game counts the dealer’s; Japanese Wikipedia and Fuda Wiki give nobody points in that case.

Question 12

Who deals first, and who deals next?

Accepted Answer

Against the computer, each side turns over a card and the earlier month deals; within one month the card worth more deals, and two plains of one month mean drawing again. Online, a fair coin flip picks the first dealer. After that the winner of each round deals the next, and after a drawn round the dealer stays. The dealer plays first.

Question 13

Why doesn’t the Rain man count towards Sankō?

Accepted Answer

Sankō (Sanko) is three Lights without the Willow Light, the Rain man (柳に小野道風). With the Rain man, four Lights make Ame Shikō (7 points) and all five make Gokō (10); the Rain man with only two other Lights is not a yaku. Nintendo’s table works the same way.

Question 14

Does the Sake cup also count as a Kasu (plain)?

Accepted Answer

Not in this game: the Chrysanthemum with Sake cup counts only as a tane (animal) card. Under Nintendo’s rules it also counts as a plain, so there nine plains plus the Sake cup already make Kasu. Some tables let it count as one or the other, but not both.

Question 15

Do Inoshikachō and Tane both count?

Accepted Answer

In this game, yes: Inoshikachō (5 points, +1 for each other tane card) and Tane (five tane cards, 1 point, +1 for each extra) both score, and the same goes for Akatan or Aotan and Tan. Nintendo’s table cancels Tane once Inoshikachō is made, and Tan once Akatan or Aotan is made. With Inoshikachō and two other tane cards that makes 8 points here and 7 under Nintendo’s rules, before any doubling.

Question 16

What are Hanami-zake and Tsukimi-zake, and what is ame-nagare?

Accepted Answer

Curtain and Sake cup make Hanami de ippai (Hanami-zake, flower-viewing sake), and Moon and Sake cup make Tsukimi de ippai (Tsukimi-zake, moon-viewing sake): 5 points each, here and in Nintendo’s rules. Some house rules cancel them because of a Willow (rain) card, ame-nagare, or a Paulownia card, kiri-nagare, and others leave them out altogether. This game always counts them.

Question 17

How many points is each yaku worth?

Accepted Answer

Gokō 10, Shikō 8, Ame Shikō 7, Sankō 5, Hanami de ippai 5, Tsukimi de ippai 5, Inoshikachō 5, Akatan 5, Aotan 5, Akatan Aotan no Chōfuku 10, Tane, Tan and Kasu 1 each, and the hand yaku Teshi and Kuttsuki 6. Inoshikachō, Akatan, Aotan, Chōfuku, Tane, Tan and Kasu add 1 point for each extra card. These are the values of Nintendo’s published table; Japanese sources sometimes count points in mon (文), a traditional unit.

Question 18

Does the score double at 7 points or at 8?

Accepted Answer

Nintendo’s rules double a round total of 7 points or more, and the Japanese rule pages cited on the house rules page describe the same rule. This game doubles at 8 or more; it is a room setting, on by default, and with it off only koi-koi calls multiply a round. So Ame Shikō (7 points) with no calls scores 7 here and 14 under Nintendo’s rules.

Question 19

What happens if my opponent scores after I call Koi-Koi?

Accepted Answer

If they call Shōbu, they win the round and your yaku score nothing. Their total is multiplied by 1 plus the number of koi-koi calls made that round by both of you, ×2 after one call and ×3 after two, and also doubled if it reaches 8 points while that room setting is on. Under Nintendo’s rules their score is doubled once.

Question 20

How many rounds is a game, and who wins?

Accepted Answer

Rooms play 6 or 12 rounds, chosen when the room is created; practice from the home page plays 6. Both players start with 25 points and the loser of each round pays the winner, at most what they have left; a player who runs out loses at once, otherwise the one with more points after the last round wins. Nintendo’s rules play 12 rounds and add up each player’s scores instead.

Question 21

Is Koi-Koi Online free?

Accepted Answer

Yes. The whole game is free to play in your browser, against the computer or online against a friend, and there is nothing to buy.

Question 22

Do I need an account?

Accepted Answer

Not to practise: games against the computer need no account. To play online you sign in with a Google account; your opponent then sees your profile name and avatar.

Question 23

How do I play with a friend online?

Accepted Answer

Sign in with Google, create a room in the lobby and send your friend the invite link or the six-character room code. A public room is listed in the lobby while you wait; a private one is not, and you can add a password to either.

Question 24

Can I play alone against the computer?

Accepted Answer

Yes. Practice games are played against the computer, Hokusai, with the same rules as online games. They run on your own device and are not counted in the rankings.

Question 25

Can my opponent or the server see my cards or cheat?

Accepted Answer

Online, both players’ devices shuffle the deck together with commutative encryption (“mental poker”), so neither your opponent nor the server can see or choose your cards. Every step of the shuffle carries a zero-knowledge proof that the other device checks before it answers, so a tampered deck is refused before anyone can learn a card from it, and both devices check every step again at the end of each round. Every move is encrypted end to end and signed by its player; the other device replays it against the rules and counter-signs it, or refuses it. A match counts in the rankings only when both devices sign the same result, so neither player can record a win the other’s device does not confirm.

Question 26

Can I play on my phone? Do I need to install an app?

Accepted Answer

Yes, it runs in the browser on phones, tablets and computers, with nothing to download. If you like, you can add it to your home screen or install it as an app from the browser, so it opens from its own icon; the app page explains how.

Question 27

Does it work offline?

Accepted Answer

Practice against the computer does, once the home page, where the game runs, has been opened on that device; installing it as an app makes that easy to reach. Online matches need an internet connection.

Question 28

Is the game available in Japanese?

Accepted Answer

Yes. The game and this site are in English and Japanese; switch with the 日本語 / English link at the top of any page. Your choice is remembered on your device.

Question 29

What personal data does the game keep?

Accepted Answer

Practice games stay on your device. When you sign in, the game keeps what online play needs: your Google sign-in, a profile name and avatar, and your rooms and match results. The privacy page lists it all.

Question 30

Is this an official Nintendo game?

Accepted Answer

No. Koi-Koi Online is an independent game and is not affiliated with Nintendo or any card maker. Nintendo is named because its published rules are often used as the reference for Koi-Koi; the card pictures come from Wikimedia Commons under the CC BY-SA 4.0 licence.

Koi-Koi questions and answers

The game