Set in the final days of the Tokugawa Shogunate, the Shogunate is using the Heaven's Song to brainwash people and rule the country. Freedom fighters are "rockers" led by Sakamoto Ryoma.

[Source: Siliconera]

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.

[Source: MyAnimeList News]