After receiving an invitation from a mysterious person, Bo-bobo and rebels decide to go to Prison Island. Upon arriving at the island, Bo-bobo gets separated from his friends. In addition to that, the island also brings together members of both the third and fourth eras of the Maruhage Empire that Bo-bobo have defeated in the past.

After receiving an invitation from a mysterious person, Bo-bobo and rebels decide to go to Prison Island. Upon arriving at the island, Bo-bobo gets separated from his friends. In addition to that, the island also brings together members of both the third and fourth eras of the Maruhage Empire that Bo-bobo have defeated in the past.