Ryouma and his companions set off on a day trip to Teradaya, a lovely hot springs inn, only for their getaway to be interrupted by a murder on the premises. The victim bears a strange number, 69, written on his leg, and working out what it means holds the answer to the case. The single-episode OVA pairs the music-driven Bakumatsu Rock cast with a whodunit plot. It never aired on television and was instead packaged with the game Bakumatsu Rock: Ultra Soul.