Bakumatsu Rock: Mystery! Onsen Kaijiken ze yo!! 2014 幕末Rock 湯煙推理劇[ミステリー]! 温泉怪事件ぜよ!!

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.