The series begins with an attack on a cruise ship at the hands of Alvida. Coby, a slave of Alvida, discovers a barrel. One of Alvida's pirates attempts to open the barrel, but a young boy emerges and accidentally hits him. The remaining pirates attack him, but the stranger stops them and says that his name is Monkey D. Luffy. Luffy drags Coby to the storage cellar of the ship, where he eats and converses with Coby, who reveals his dream of being a marine. Alvida confronts Luffy, but he escapes and knocks her pirate crew down with his Devil Fruit power. Luffy explains that he ate the Gum-Gum Fruit, therefore he has the properties of rubber. Coby, inspired by Luffy, stands up for himself when Alvida confronts them. Luffy uses his Gum-Gum Pistol technique on Alvida. Luffy and Coby sail away in a "borrowed" boat from Alvida's crew. Luffy asks about the pirate hunter Coby mentioned earlier. Coby says that he was captured by the Marines, and Luffy announces his intention of asking him to join his crew.

Luffy and Coby arrive at an island with a large Marine base, where Luffy discovers the swordsman, Roronoa Zoro tied to a pole. Rika, a young girl, offers Zoro some rice balls that she made herself. Helmeppo, the son of Marine Captain Morgan, discovers this and has Rika thrown out. Luffy asks Zoro to join his crew, but Zoro refuses and has Luffy give him the rice balls. Luffy and Coby meet Rika in town, who is happy to hear that Zoro enjoyed the rice balls. She tells them how Helmeppo brought his vicious pet dog into their bar and that Zoro knocked it out to protect everyone inside. He then made a deal with Helmeppo: if he can survive being tied to a pole with no food or water for thirty days, then Helmeppo will spare the little girl and her mother. However, Helmeppo says that he will execute Zoro the next day despite his word. Luffy punches him, and Helmeppo runs off to tell his father. While Luffy invades the Navy base to find Zoro's swords, Coby attempts to untie Zoro and explains the situation to him. Morgan orders that they are both to be executed. The soldiers open fire, but before the bullets can reach them, Luffy leaps from the base and uses his rubber body to block the bullets.

Luffy hands the three swords to Zoro in exchange for Zoro joining his crew. Luffy and Morgan engage in battle. All of Morgan's attacks miss and Luffy knocks Morgan to the ground. Meanwhile, Helmeppo takes Coby hostage. But Coby declares that he will not stand in the way of Luffy's dream, even if it means death. Luffy strikes Helmeppo, while Zoro takes out Morgan right before he can kill Luffy. As Morgan collapses, the Marines toss their weapons into the air in celebration of their captain's defeat. Later, Luffy, Zoro, and Coby are in the town restaurant with Rika and her mom. Marines step into the restaurant, and as Luffy and Zoro are pirates, they must leave the island immediately. Luffy and Zoro get ready to go, and the head of the Marines asks if Coby is with them. Luffy goes on to explain that Coby spent time aboard Alvida's pirate ship as her slave, and this makes Coby angry as it will ruin his chances of enrolling in the Marines. Coby punches Luffy, in response Luffy beats Coby to near death. The Marines see Coby is not with them, and so order Luffy and Zoro to leave. As they do, Coby asks to join the Marines, and is accepted. Outside, Luffy and Zoro climb into their boat, and as they set sail, the Marines salute them for saving the town, including Coby. Coby vows to meet Luffy again, as a Marine meeting a pirate.

In a flashback, a seven-year-old Luffy sits in a bar filled with the pirate crew of the "Red-Haired" Shanks, begging him to take him out to sea. But the pirate captain refuses. A bandit named Higuma enters and orders several barrels of booze. Shanks offers him the last bottle but Higuma smashes it and humiliates Shanks. After the bandit leaves the bar, all of the pirates start to laugh. Luffy gets angry that Shanks did not fight back and in a huff eats a purple fruit lying on the bar. Shanks notices this and tries to make Luffy spit it out, but it was too late. Shanks tells Luffy that he just ate the Gum Gum Fruit, a Devil Fruit, and now he is a rubber man and won't be able to ever swim again. Later, Luffy gets attacked by Higuma and his bandits. He is about to be killed, when Shanks and his crew arrive and effortlessly defeat Higuma's men. Frightened, Higuma throws down a smoke bomb and makes his escape, taking Luffy with him. He flees out to sea in a boat. There he throws the non-swimmer into the water. As Higuma laughs at Luffy's plight, a Sea King appears behind him and devours him whole. The sea monster then goes for Luffy, but Shanks stops the sea monster as it takes a bite, and with one look, drives the beast away. Luffy clutches Shanks and starts crying, since Shanks' arm was bitten off by the creature. Shanks replies that it is fine, as long as Luffy is safe. As the pirates get ready to leave, Luffy decides he will become a pirate on his own, that he will gather a crew that will beat Shanks', and that he will become King of the Pirates. Shanks gives his straw hat to Luffy and tells him to return it some day, as a great pirate. Back in the present, Luffy slingshots into the sky to catch a bird. Instead he is caught himself. Zoro, now alone in their boat, tries to keep up, paddling. On his way he picks up three castaways from Buggy's crew. The bird, carrying Luffy flies over a town, where it is shot down by Buggy's men. Luffy falls down and lands right in front of Nami, who is running away from Buggy's crew for stealing their precious map to the Grand Line.

Nami pretends that Luffy is her boss, using the distraction to escape from Buggy's men. After Luffy beats them, she asks him to join her. Then Luffy finds out that she is a navigator, and asks her to join his crew of pirates. As she hates pirates, she refuses. Then she tricks Luffy into letting himself be tied up and brought to Buggy, where he is locked up in a small cage, while Nami fakes joining Buggy's crew. As proof of loyalty, Buggy demands of Nami to kill Luffy, but she cannot bring herself to do it. As Buggy's pirates attack her, Zoro arrives to save his captain and her. Buggy recognizes Zoro as the pirate hunter and attacks him. Zoro cuts Buggy into pieces. Believing Buggy to be dead, he sheaths his swords and is stabbed in the back. The wound puts Zoro at a disadvantage. He picks up the cage with Luffy inside and the three escape.

Still trapped in the cage, Luffy meets a small dog named Chouchou guarding his master's store, despite knowing that his owner is dead. Mohji the Beast Tamer's lion, Ritchie, inadvertently breaks Luffy's cage open, and sends him flying. Chouchou tries to protect the store, but is no match for the much stronger Ritchie, and Mohji burns the store down. Angered by Mohji destroying what the dog finds precious, Luffy mercilessly punches him out. Moved by Luffy's concern for the dog, Nami agrees to work with Luffy for the time being.

Enraged by the actions of Buggy's crew, the city's Mayor Boodle rushes to fight Buggy himself, but the Straw Hat Pirates come to his rescue, Luffy knocking him out to prevent him from getting himself killed. Zoro fights Cabaji, despite still being wounded from his previous encounter with Buggy, and defeats him. Nami leaves to search for the map to the Grand Line. Luffy begins fighting Buggy, who knows that he can injure Luffy's rubber body by cutting him, and enrages him by damaging his straw hat.

When Luffy, Zoro, and Nami land on another island, Usopp appears to greet them, with three children hiding in the bushes. After a failed attempt on Usopp's part to scare the pirates away, they talk about Shanks and his marksman Yasopp, Usopp's father. Usopp brings them to a restaurant, where after a meal, he leaves them to head for a mansion outside town. The mansion belongs to Kaya, a sickly young woman. She and Klahadore, her butler, talk about Usopp and Klahadore forbids her to see him. Usopp comes anyway and he tells Kaya a story about fighting a giant goldfish with droppings the size of islands. Back at the restaurant, Usopp's small friends, the Usopp Pirates enter in search of their captain. They bring Luffy, Zoro, and Nami to Kaya's mansion, and tell them how Usopp tells Kaya lies to cheer her up since her parents died and she became ill. Luffy decides they should ask her for a ship and as there are bodyguards guarding the gate, he slingshots the whole group over the fence. They crash into the ground near Usopp, and as they get up, Klahadore comes out and calls them intruders.

At Kaya's mansion, Klahadore goes on about how Usopp's father is a filthy pirate, making Usopp livid enough to punch him in the face. Klahadore continues taunting Usopp, who eventually leaves. Later, Kaya is crying in her room. Klahadore enters to bring her a meal and reminds her of the day he came to the mansion, when he was battered and her father took him in. He then claims that if anything happened to Kaya, he would not forgive himself. The Usopp Pirates, Nami, and Zoro encounter Jango, who claims to be only a passing hypnotist. He then hypnotizes the Usopp Pirates — and accidentally himself — into falling asleep in the middle of the road. Later, by a cliff overlooking the ocean, Luffy and Usopp witness Jango and Klahadore — whose true identity turns out to be that of the infamous pirate Captain Kuro — plotting a raid of the village, and Kaya's murder. Luffy yells at them not to get rid of Kaya, but Jango uses his hypnotism to put Luffy to sleep, causing him to fall off the cliff. He lands on his head and appears to be dead. They do not worry about Usopp knowing, because of his reputation as a liar.

Zoro, Nami, and the Usopp Pirates are still waiting around for Luffy and Usopp. The Usopp Pirates mention how Usopp always goes to the coast. They then spot Usopp running up to them, but he does not respond to any of their questions and runs right past them. Usopp is unable to convince the villagers that pirates are coming and that they have to abandon their homes. Meanwhile, Zoro and the others find Luffy. At Kaya's mansion, Merry shows Kaya the glasses that she got him to buy for Klahadore's third year of being a caretaker. Usopp is unable to convince Kaya of Kuro's assassination attempt and leaves, but gets shot by Merry in the process. Kuro announces his plans to attack the village at dawn. At sunset, Usopp remembers the stories he would tell Kaya, when Luffy and the Usopp Pirates arrive. Usopp tells them about Kuro's plan, but then says that he was joking about it. The Usopp pirates abandon him. Nami asks Usopp why he said he made everything up. Usopp replies that it is because he is a liar. He says how he loves the village and wants to protect it, so he will stand against the pirates. Luffy, Zoro, and Nami decide to join him, and so Usopp stands up, declaring that even though he is scared, he will fight.

Usopp, Luffy, Zoro, and Nami formulate a plan on the slope for when the pirates come. Meanwhile, Kuro breaks the glasses Kaya gave him and injures Merry with his clawed glove. Kuro then steps into Kaya's room, and he holds his blood-stained claw over Kaya's head, remembering the deed he has to commit the following day. By the coast, the Black Cat Pirates's ship approaches Syrup Village. Jango reiterates the plan to his men. Meanwhile, Luffy, Usopp, Zoro, and Nami stand on the slope leading to the village, and have poured a barrel of oil on it to make it slippery. The plan is that when the Black Cat Pirates slip on the oil, the four will spring out and attack them. Dawn breaks, and so the Black Cat Pirates land on the coast, spotting Luffy's boat. At that moment, Luffy and the others are waiting for the pirates as the sun has now risen, and Nami hears the pirates coming from the north. Usopp notes that there is an identical slope at the north end of the village, and they realize they are at the wrong coast. Panicking, Nami then realizes that their ship is located at the north coast, and their treasure will be robbed by the pirates. Luffy and Usopp take off running for the coast. Zoro and Nami start to leave, but Nami slips on the oil and drags Zoro down the slope, stepping on him to climb back up. Zoro is unable to get up the slippery slope, and he slides to the bottom, but eventually uses his swords to pull his way up. At the north coast, Usopp arrives, surprised that Luffy hasn't come yet - Luffy is now lost. The Black Cat Pirates arrive, and Usopp stands up to them, but realizes he can't beat them by himself. He sees the pirates taking the treasure from the Straw Hats's ship, and he says that the treasure belongs to him, and he'll give it to them if they leave. Jango decides to hypnotize Usopp instead, but an enraged Nami arrives in the nick of time and whacks Usopp in the head, knocking him over, refusing to give up her treasure. Usopp then reports that Luffy has not arrived yet, and is probably lost. The Black Cat Pirates then charge, and Usopp stands up to them, but they knock him down swiftly. Usopp struggles to fight them, but there are far too many. He is shocked when they are all sent flying back, and sees that Luffy and Zoro have arrived. Zoro yells at Nami about leaving him there, and Luffy yells at Usopp for not telling him which way was north. However, united, the four face off against the invading Black Cat Pirates.

Jango kneels beside the fallen pirates and starts to hypnotize them. Once the hypnotism takes effect, the pirates became wild and ravenous, and foaming at their mouths, they charge at the Straw Hats. One pounds down a cliff with his fist. Zoro says that he and Luffy will handle it, but Luffy was also hypnotized, becoming a wild animal himself. Luffy charges down the slope and uses his Gum-Gum Gatling technique to plow through the pirates with ease. Luffy keeps charging, and soon runs past the pirates, causing Jango to fear that he will be the next target. Luffy takes the bow of Kuro's ship in an attempt to kill him, but Jango hypnotizes Luffy, and so Luffy falls asleep, the bow falling on top of him and squishing him as he does this. With Luffy out of the way, Jango prepares for the next attack. Seeing the pirates are defeated, he calls for Siam and Butchie and orders them to attack. They turn out to be cowards, but after some heavy persuasion they charge for Zoro. Zoro blocks their claws with his sword, and engages in a great fight with the two Meowban Brothers. Zoro slashes Siam through the lowersection, but finds out Siam has a very thin waist. He sits on top of Zoro and Buchie leaps down, but Zoro manages to avoid the bone-crushing attack that leaves a crater. Butchie then uses his cat-like abilities to steal Zoro's two swords, and throws them away. Zoro has no chance to grab them and faces another assault by the Nyaban Brothers. Usopp decides to help and fires at the brothers, but Zoro blocks it with his back, yelling at Nami and Usopp to not get themselves killed. Nami then runs for Zoro's swords, picking them up, but Jango reacts swiftly and slashes her in the shoulder with his chakram. Just as Jango and the others are about to kill the Straw Hats, Kuro appears, enraged that his plan has been completely foiled.

The episode begins with Kuro standing impatiently. Siam and Butchie decide that Kuro, having been inactive for three years, has lost his edge, and that they can defeat him. They charge at Kuro but only swing at thin air, and Kuro appears behind them, holding his claws to their necks. He says that everyone has five minutes to finish their job, or he will kill them all. He releases the Meowban Brothers, pushing them so that they can continue their battle with Zoro. However, Nami sees her chance and kicks Zoro's swords through the air. Zoro catches them, and as the Meowban Brothers charge at him he unleashes a great Toragiri, taking both of them down with one mighty swing. He turns to Kuro and declares he won't even need five minutes. Nami realizes how dangerous Kuro is, and so runs to wake up Luffy. As she runs, Jango spots her, and hurls a chakram at her. Nami turns and steps on Luffy's face, waking up Luffy abruptly. He springs up, pulling Nami down just as the chakram strikes him right in the mouth. Luffy stays standing, though, and he breaks the chakram with his teeth. He then sees Nami is wounded, and furious, prepares for battle with Kuro. At the mansion, Kaya wakes up from a nightmare, and she heads down the stairs to find Merry leaning against the wall, bloody and wounded. Merry explains the whole situation to Kaya, how Kuro is planning to kill her and take her money in a will. Kaya realizes that Usopp was telling the truth the entire time, and so she puts on her overcoat and sets out. She arrives at the top of the slope, and tells Kuro to stop immediately, and that Merry told her everything. Kuro turns to her and wonders why Merry isn't dead, and Kaya sees the state Usopp is in. Usopp charges in and aims a punch at Kuro's face, but Kuro avoids the swing and so Usopp careens into the ground. Kaya then pulls out a gun and points it at Kuro, ordering him to leave the village. Kuro reminds Kaya of the fun times they had together, and Kaya hesitates. Kuro takes the gun from Kaya's hands, knowing she won't shoot, and he drops it to the ground. Usopp picks up the gun and fires at Kuro, but Kuro sidesteps the shot and knocks Usopp down. From out of nowhere flies Luffy's fist, striking Kuro in the face. As Kuro falls back, Luffy retracts his Gum-Gum Pistol and declares that he has a hundred more where that came from.