Bakumatsu Rock: Mystery! Onsen Kaijiken ze yo!!

幕末ばくまつRock 湯煙ゆけむり推理すいり劇げき[ミステリー]! 温泉おんせん怪かい事件じけんぜよ!!

An incident has led to someone's death at Teradaya, which the gang went to for a day trip. A "69" on the victim's leg will be the key to solving the mystery.