Kokushi Musou

Conditions

• The hand must contain one of each of the 13 terminal and honor tiles: 1m, 9m, 1p, 9p, 1s, 9s, 1z (East), 2z (South), 3z (West), 4z (North), 5z (Haku), 6z (Hatsu), 7z (Chun)
• One of these 13 tiles must appear twice to form the pair (any of the 13 can be the duplicate)
• The hand must be closed — no open calls allowed
• Does not follow the standard 4 melds + 1 pair structure; it is a special winning pattern
• Some rulesets award double yakuman if you win on a 13-sided wait (waiting on all 13 unique tiles when you have one of each and need any duplicate)

Strategy Tips

• Kokushi is most viable when your starting hand already contains 8 or more different terminals and honors. If you have fewer than that, the odds of collecting all 13 types drop sharply and you are better off pursuing a standard hand.
• Because kokushi uses only terminals and honors, your discards will be almost entirely middle tiles (2-8), which clearly signals what you are doing. Experienced opponents will stop discarding isolated terminals and honors once they read your pattern, so speed matters.
• The 13-sided wait (where you have all 13 unique tiles and need any one of them as a duplicate) is one of the strongest waits in the game because almost any terminal or honor tile completes it. If you reach tenpai with this wait, your winning chances are excellent.