A group of pirates lead by Alvida plunder a ship, only to find a barrel which contains a strange boy named Luffy. Luffy is on a mission to find the legendary treasure "One Piece" and he befriends the ship's cabin-boy, Coby, who actually wants to become a marine officer. Luffy defeats Alvida and the two journey on in search of crewmates.

Luffy and Coby 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.

Luffy convinces Zoro to join his crew, but they must first defeat Captain Morgan. After freeing the island from Morgan's oppressive rule, Coby is accepted as a marine while the other two continue on their journey.

Out on the sea, Luffy almost loses his hat and reflects on his past, and how a pirate named Shanks influenced him. Afterwards, Luffy meets Nami, and Buggy the Clown's men.

In order to save herself and steal a map to the Grand Line, Nami tricks Luffy into allowing her to turn him over to Buggy.

Mohji and Richie show up for revenge after Buggy's humiliating defeat in the previous episode, and Luffy meets a small dog guarding his master's store, even though he knows that he is long dead.

Enraged by the actions of Buggy's crew, the city's mayor rushes to fight Buggy himself, but the Straw Hat Pirates come to his rescue. Zoro fights Cabaji, despite still being wounded from his previous encounter with Buggy, while Luffy faces the clown pirate himself and Nami searches for the map to the Grand Line.

Buggy's link to Shanks is revealed, and when he rips the straw hat Shanks gave Luffy, his rage knows no bounds. Who will win in this clash between Devil Fruit users?