yakyūken; strip rock-paper-scissors
A game similar to strip poker, but using rock-paper-scissors (janken) instead of cards. The loser removes an article of clothing. Often associated with drinking parties or comedic contexts.
On the night of the training camp, we all got excited playing yakyūken.
I've seen yakyūken on a TV variety show.
Named after a baseball-themed call-and-response dance devised in Matsuyama in 1924 and later adapted into a rock-paper-scissors game. The stripping game is a later entertainment variant.