Bakumatsu Rock: Mystery! Onsen Kaijiken ze yo!!

Unaired OVA bundled with the game <i>Bakumatsu Rock: Ultra Soul</i>.<br> <br> 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.<br> <br> (Source: MAL News)