Kai-oi
Kai-oi — Shell Matching is a traditional game for 1–6 players, about 10 minutes. Find the ground shell matching the drawn shell and collect the most pairs.
Kai-oi in 30 seconds
StartCompare the shell patterns.
MiddleChoose a shell, then Check.
EndMost pairs wins.
- Set upGround shells form a ring, patterned sides up. One drawn shell sits in the center.
- Take turnsChoose a ground shell. Check places it beside the drawn shell, then shows the result after 3 seconds. A match earns another turn; a miss passes the turn.
- EndFinish when no drawn shells remain.
- WinMost pairs wins. Players tied for first all win.
At a glance
| Item | This game |
|---|---|
| Players | 1–6 players |
| Play time | About 10 min |
| Type | Board |
| Ranked play | No |
| Practice against the CPU | Yes |
| Price | Free (no account needed) |
| Rights holder | A public-domain classic game |
| Last updated | 2026-11-11 |
How to play Kai-oi online with friends
- Tap "Play with friends"A party is created with a 6-character code. No account is needed.
- Send a link or QR codeShare it on LINE, or just read the code aloud.
- Everyone opens it in a browserOnce 1–6 players have joined, the host taps "Start".
Rule highlights
Setup, play, winning, and house rules
Setup
- Each real clam supplies two matching halves: a ground shell and a drawn shell.
- Use 26 pairs, or choose a short 12-pair game. Both orders are shuffled each game.
How to play
- Choose a ground shell to mark its original place with a hand. Everyone, including watchers, sees the same hand. Change your choice before Check.
- Press Check to move it beside the drawn shell. Wait 3 seconds after they line up for a circle and Match, or a cross and No match. A match earns a pair and another turn; a miss passes the turn with the same drawn shell.
- Collected places stay empty. The default limit is 20 seconds, shown by a shrinking ring and a number. At the deadline, a selected shell goes to Check; no choice costs one try and passes the turn.
Winning
- When no drawn shells remain, most pairs wins. All players tied for first win; an all-player tie is a draw.
- Solo play counts presses of Check, including timeouts. Aim for fewer tries. Your personal best is stored on this device.
- The shells in this game are photos of clams bought at AEON Higashikurume.
House rules
| Name | Description | Default | Changeable |
|---|---|---|---|
| Pairs | Choose 12 pairs for a shorter game. | 26 pairs | Yes |
| Time limit | At the limit, check the selected shell; without a choice, pass the turn. | 20 seconds | Yes |
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FAQ
How many players?
One to six. Play against one computer opponent, or play solo for the fewest tries.
How long?
About 8–12 minutes with 26 pairs, or 3–5 minutes with 12.
When do shells appear side by side?
A hand marks your choice in its original place. You can change it before Check. Check places it beside the drawn shell; the result appears 3 seconds later.
Can I play on a phone?
Yes. No app is needed — just open it in a browser. You can join the same party as people on a PC or tablet.
Can two people play?
Yes. This game supports 2 or more players.
Can I play against the computer (CPU)?
Yes. You can play against computer opponents without inviting anyone.
Can I play online with friends far away?
Yes. Start a party and send its invite link. Friends can join in their browsers without signing up.
Is there an app?
This is a free app that runs in your browser. No installation is needed.
Rights holder and physical edition
This is a public-domain classic game. The rules follow the standard reference rules.
Related games
Same type (Board)
Same player count
- Online games for two players
- Games for three players
- Games for 4 players online
- Games for six or eight players
Last updated 2026-11-11 · Run by Qdan, Inc.