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?

Nami form an alliance becoming the navigator of the crew, but not a full member yet. They arrive in Syrup Village looking for a suitable ship. On this island they know the liar Usopp, who also has ties to the Shanx.

When trying to convince his rich friend, Kaya, to give the Straw Hats a ship, Usopp is told to stay away from her by her caretaker, Klahadore. However, when Usopp and Luffy later see him conversing with a strange man, they learn of a plot to kill Kaya.

After learning of Captain Kuro's evil plan, Usopp runs back to the village to warn Kaya, only to find that after all his years of lying no one believes him.

Usopp resolves to keep his story of pirates attacking the town a lie by making sure none reach it. Luffy, Zoro, Nami, and Usopp then try to keep the Black Cat Pirates at bay.

The Straw Hats manage to take out most of the opposing Black Cat Pirates, so Jango orders the Nyaban Brothers to attack. Meanwhile, after getting hypnotized by Jango, Luffy gets himself stuck under the collapsed mast of the Black Cat Pirates' ship.

Captain Kuro himself arrives at the scene, and with Zoro too injured to fight, Luffy being incapacitated, and the other two being too weak to handle him, things seem hopeless. However, Kaya herself appears to bargain with Kuro.

Zoro and Buchi (of the Nyaban Brothers) face off once again as Luffy and Kuro begin their fight. Usopp orders the Usopp Pirates to run away with Kaya, but Jango goes after them. A flashback reveals how Captain Kuro faked his death with Captain Morgan and how he became Kaya's butler.

As the fight between Luffy and Kuro is close to an end, the Usopp Pirates do their best to avoid Jango.

Kuro's ultimate attack, "Shakushi", attacks everything in the area, whether friend or foe, and Luffy becomes enraged by his lack of regard for his crew. Will Luffy's determination overcome Kuro's sheer speed?

With Usopp now in the crew and a new ship, the Going Merry, under their command, the Straw Hats head to an island said to hold a fabled treasure, only to encounter a strange man stuck in a treasure box that has also been looking for this treasure.

While Usopp & Luffy fool around with the ship's cannon one day, Zoro dreams about his childhood and the promise he made to Kuina.

The crew meets Johnny and Yosaku, Zoro's former companions, and they set sail for the Baratie restaurant in search of a cook.

Sanji, a cook at the Baratie, helps a starving pirate named Gin. Luffy begins his job as a waiter to pay for the damage he did to the Baratie, and tries to convince Sanji to join his crew.

Gin returns to the Baratie with his also-starving captain, Don Krieg, to whom Sanji once more gives food, but Don Krieg betrays the cook once he regains his energy.

It is revealed that Chef Zeff was a great pirate known as Red Leg Zeff. Gin explains the catastrophe the fleet met in Grand Line when they encountered Hawk-Eyes Mihawk, and Krieg attempts to take control of the Baratie.

As Nami steals the Going Merry, Mihawk has returned to finish the job, but Zoro challenges him to a duel in order to achieve his dream.

Mihawk leaves after defeating Zoro, so Krieg continues his invasion and has Pearl, one of his stronger crewmates, attack, and Sanji reveals his fighting skills. Meanwhile Johnny and Yosaku leave with Usopp and the wounded Zoro to go after Nami.