Luffy is found floating at sea by a cruise ship. After repelling an invasion by the Alvida Pirates, he meets a new ally, their chore boy Koby.
Luffy and Koby find Zoro captured in Shells Town's Marine base, with the Marines intending to execute him. Luffy and Koby work together to retrieve Zoro's katanas, as well as confront the tyrannical Marine Captain Morgan and his son Helmeppo.
Luffy and Zoro battle and defeat Morgan, Helmeppo and the Marines. Koby parts ways with Luffy to join the Marines, and Zoro joins Luffy's crew as a permanent crew member.
The significance of Luffy's straw hat is explained as the hat was entrusted to him by his idol, Shanks. Luffy then accidentally finds himself in Orange Town, territory of the pirate Buggy.
Luffy, Nami, and Zoro confront Buggy the Clown. Buggy threatens to fire a Buggy Ball at Luffy, but this attack is redirected back at his men.
Luffy defends himself from Buggy's assassin, Beast Tamer Mohji and his lion Richie. Allying himself with the town's mayor as well as a dog, the Straw Hats return to Buggy's base to confront him.
Zoro takes on Buggy's acrobat and chief of staff, Cabaji, engaging in a one-on-one sword fight. After Zoro emerges victorious, Luffy battles against Buggy, where his straw hat is damaged by Buggy's attacks.