Shell Island

Luffy, Mirabel and Koby arrive at Shell Island, a Marine base. They meet the bounty hunter Roronoa Zoro, held under arrest by the infamous marine, Captain Morgan, and his son Helmeppo.

AKA

Mirabel, Luffy and Koby find Zoro captured in Shells Town's Marine base, with the Marines intending to execute him. Luffy, Mirabel and Koby work together to retrieve Zoro's katanas, as well as confront the tyrannical Marine Captain Morgan and his son Helmeppo.