Riichi Mahjong Yaku
Thirteen Orphans
Also known as: Kokushi Musou · Kokushi · 国士無双
One of every terminal and honor tile, plus a duplicate of any one of those thirteen tiles.
Yaku value
Closed hand
Yakuman
Open hand
Closed only
Requirements
Collect the six terminals and seven honors, then pair any one of them. The hand is closed and does not use the normal four-groups-and-a-pair structure.
Common scoring mistake
Only terminals and honors may appear. Some rules award a double Yakuman for the thirteen-sided wait, but this depends on the table rules.
Values follow common modern Riichi rules. Local and tournament rules may differ, especially for double Yakuman.