Tonpuusen 「東風戦」 consists of a game that ends after the east round. A full hanchan of the game may take a long time, anywhere between one hour to an hour and a half even among fast players. An east round only game may naturally cut the duration in half. While a full hanchan may extend into the overtime west round if necessary, the south round in this case works in the same manner.
Strategy differences compared to hanchan
Under hanchan, players have the opportunity to be oya (dealer) twice. In hanchan, however, that is not the case. Everyone has the chance to be dealer only once.
- Tonpuusen in Japanese Wikipedia