Thirteen Orphans

Thirteen Orphans (Kokushi Musou in Japanese Riichi, also called the Thirteen Wonders) is a special closed hand built entirely from terminals and honors. It requires one of each of the thirteen unique 'orphan' tiles — the 1 and 9 of each suit (1m, 9m, 1p, 9p, 1s, 9s) plus all seven honors (the four winds East, South, West, North and the three dragons) — with one of those thirteen tiles duplicated to form the pair. Like seven pairs, it ignores the normal meld structure entirely.

It is among the most celebrated hands in the game. In Riichi it is a yakuman, paying the limit (32000 for a non-dealer, 48000 for the dealer) and requiring a fully concealed hand. A standout feature is its thirteen-sided wait: if a player holds all thirteen distinct orphans with no pair yet (a 13-tile tenpai), they can win on any of the thirteen tiles, the widest wait in the game. Many rulesets recognize this 'thirteen-wait' version as a double yakuman. Hong Kong mahjong scores it as a limit hand, and Chinese MCR awards 'Thirteen Orphans' a high fixed value.

A completed example: 1m, 9m, 1p, 9p, 1s, 9s, East, South, West, North, white dragon, green dragon, and a pair of red dragon. Because every tile is a terminal or honor, the hand is incompatible with any sequence and with tanyao (all-simples) hands. A common confusion is assuming you can substitute an 8 or 2 — only the actual 1s, 9s, and honors qualify. Strategically it is usually pursued only when a hand starts heavy with honors and terminals, since chasing it from a mixed hand is far too slow, and it must remain concealed to count in Riichi.