A man is handcuffed and in front of him there are two other men with swords, crossing into an "X". There was once a man who took everything in the world: wealth, fame and power, known as Pirate King Gold Roger. The pirate's last words drove people throughout the world to the sea. Roger announces that if someone wants his treasure, he or she can have it, saying that he left everything "there". Roger is executed, and the entire crowd, including a man with a pirate symbol on his hand, is cheering. The world has entered the Golden Age of Piracy.
In a small seaport village, a pirate ship landed almost one year ago. The east wind blows. It is a small peaceful village. A boy is standing on the ship's figurehead. A man asks Luffy what he is doing. The child's full name is revealed to be Monkey D. Luffy. He has a knife in his left hand, and he is wearing a shirt with "ANCHOR" written on it. He announces that he is not joking this time as he had enough, and he decides to prove it for everyone. The man is wearing a straw hat and he tells Luffy to go for it to see what he is going to do. Another man claims that the kid is going to do something funny again. The child stabs himself with the knife right under his eye, screaming in pain. All the pirates are surprised because of this. The first man shouts asking Luffy what he is doing.
In the village, the pirates and the boy have gathered in the Partys Bar. A pirate proposes to drink and celebrate to Luffy's craziness and to their greatness. Inside the bar, all the men are drinking and eating. A fat man is drinking straight from a barrel of beer. A monkey can be seen dancing in the background. One of the pirates laughs and tells everyone to drink. Another man asks to bring him more sake. Two other men are fighting over a piece of meat. The first one calls the other one an idiot and claims that it is his meat. The second one tells the first to shut up claiming that it is his. A third man tells both of them to stop because it is shameful to fight while they are drunk.
Luffy is now patched up, but he is almost crying, claiming that it did not hurt. The man with the straw hat calls the boy a liar and tells him to not do something so stupid again. The child boasts that he is not afraid of pain and asks the man to bring him to the sea the next time because he also wants to be a pirate. The man claims that Luffy is not ready to be a pirate, explaining that not being able to swim is a pirate's greatest weakness. The man is revealed to be the pirate leader called "Red-Haired Shanks". The boy boasts that he will be fine as long as he stays on the board and that his fighting is good, saying that he has trained and that his punch is as strong as pistol fire. Shanks doubts Luffy's latter claim in a bored tone. The child gets angry at the man because of his tone.
Many of the pirates are standing in a line, dancing with the fat man from before in the middle. A man on his left is wearing a kerchief with "Yasopp" written on it. One of the men observes that Luffy is unhappy. Another tells him to be happy to face anything. Another affirms that the life of a pirate is great. Another tells him that the sea is very wide, so he can go to any island and adventure. Another claims that nothing is greater than freedom. Luffy is fascinated with the pirates' words. Shanks requests that the men do not give the boy dumb ideas. The fat man argues that it is the truth. Another man confirms. Another pirate suggests to the captain that they take the child one time, since it is not a big deal. Another man and Luffy agree. Shanks orders that next time one of his subordinates shall get off the ship and let the boy replace him. Hearing this, the men turn away, while one of them comments that they said enough and that they should drink. Luffy gets angry and asks the group what kind of friends they are.
Shanks claims that the most important thing is that the child is still too young and that he will reconsider taking him in ten years. The kid boasts that he is a man. The red-haired man calms him down and gives him a glass of juice. The boy happily accepts and drinks it. Shanks starts laughing to the point of tears, proving that Luffy is still a kid. Luffy is angry at the trick.
Luffy becomes depressed that Shanks does not let him join the crew despite the fact that the boy cut himself today. The bartender can be seen in the background. A smoking man tries to explain to Luffy that he should try to understand the captain's feelings since he is their leader. The man continues and says that the captain knows that the life of a pirate is interesting, but it is also very dangerous. A wanted poster of Mikio Itoo can be seen in the background on a wall. The man claims that his captain does not purposely tease the boy's ambition of becoming a pirate. Luffy thinks Shanks is not taking him serious, which Shanks proves by mocking him again.
The bartender observes that the red-haired man is very happy. Shanks replies that making fun of the boy is his joy. Luffy suggests again to the smoking man that the captain is not taking him seriously. The bartender's name is revealed to be Makino. She holds a barrel of beer and asks the kid if he wants to eat. Luffy claims that he will pay with his treasure. Shanks doubts the existence of Luffy's treasure and calls him a liar. The boy denies, saying that he will become a pirate and pay her with the treasure he finds. Makino replies that she will be waiting, and the kid starts laughing. Luffy is waiting with a fork and knife in his hands.
Finally, Makino brings Luffy and Shanks their meals. As the boy is struggling to bite in a big piece of meat, he raises the question of how long the crew will be staying. The red-haired man comments that it has been almost a year since they have made the town their base, so he is thinking of taking a few more trips and then leave and head north. Luffy manages to bite in his piece of meat. Luffy is thinking for a moment, and Makino looks at him, almost feeling sorry for the child. As the bartender is washing some dishes, Luffy boasts that he will learn how to swim by then, and Shanks wishes him good luck.
Suddenly, a man kicks down one of the doors of the bar. The whole place goes silent. The man enters the bar along with a group behind him and excuses himself. He observes the group partying, and mentions that it is his first time seeing pirates, remaining unimpressed. The fat man and the smoking man are unfazed by this sudden appearance. Meanwhile, Luffy is eating a strange fruit and is confused. The strange man walks towards the bartender, as Shanks is sitting nearby and holding a bottle of sake. The men behind him are all wearing similar looking outfits. He claims that they are bandits and that they are not there to cause trouble, since they only want to buy ten barrels of sake. The man is revealed to be the leader of the bandits, called Higuma. However, Makino tells the bandit that the bar is out of alcohol. The man looks back toward the pirates, thinking it is strange, and asks what are the other men drinking. He sarcastically asks if it is water. The bartender confirms that the pirates are drinking sake, but that is all which is left. Shanks is sorry for the man because his group drank all the alcohol, so he offers him the last bottle that he was holding earlier. Higuma looks displeased, so he smashes the bottle, breaking it into pieces and spilling the sake on the red-haired man. Luffy gets down from his seat that was near Shanks. Makino is frightened at the situation, while the bandits are amused. The smoking man is unfazed, and the boy is surprised. The bandit leader is unsatisfied of one bottle and asks the pirate if he is unaware of the bandit's reputation. The red-haired man is upset that the floor is all wet. Higuma brings out his wanted poster of 
8,000,000, claiming that he is one of the prime fugitives there, since he killed 56 people and tells Shanks to not mess with him again because mountain bandits and pirates do not have good relationships. The red-haired pirate ignores the bandit, picks up a large piece of the bottle from the ground, tells Makino that he is sorry for the mess and asks her for a mop, saying that he will clean. Higuma takes out his sword and cuts the table along with the plates on it, saying that since the red-haired man enjoys cleaning, he can now enjoy it more. Convinced that Shanks is a coward, Higuma leaves the bar. Outside, two citizens are seen hiding behind a building. Convinced that the town is pathetic, since it does not even have alcohol, the bandit leader decides to go to the next town.
Afterwards, as Makino tries to see if the red-haired man is hurt, Shanks and his crew laugh at his humiliation. The fat man thinks that the captain looked very silly. Angered by their attitude, Luffy asks the group why they are laughing, since the situation was very disgraceful. The kid thinks they should have fought the bandits, despite the fact that they had more people. The boy thinks that someone that laughs after getting picked on is not a man, nor a pirate. Shanks tells Luffy that he understands his feelings, but there is no reason to get worked up over a bottle of alcohol. As Luffy turns to go away, Shanks grabs his arm to stop him and tells him to stay. However, the boy tells him that he doesn't want to see him again, since he is a coward. As the kid moves away, his arm stretches, to everyone's surprise, including the kerchief man. The fat man looks into a box, and everyone is surprised, saying that the Gomu Gomu no Mi that they got from an enemy ship is not there. The fat man is sweating and shows Luffy a drawing of the fruit he was eating earlier, and asks him if he ate that. Luffy affirms, asking if that was not dessert, although it tasted badly. Shanks goes in front of the boy and explains that that was the Gomu Gomu no Mi, one of the devil fruits and one of the rarest treasures in the sea, that anyone who eats it turns into a rubber human and will never be able to swim. Luffy is surprised and Shanks calls him an idiot.
Later, Luffy visits UO to buy some fish. The storekeeper and his wife are happy to see the boy. The store owner says that he looks happy, asks him if the pirates left him behind again and mentions that the kid cannot swim anymore. Luffy claims that he is going to be a pirate that doesn't fall into the sea. The boy stretches his cheeks, making them look like a big smile and he claims that he became happier after eating the Gomu Gomu no Mi. An old man asks what is so good about having a rubber body. He complains that everyone in the town thinks that Luffy's new ability is cool, but he does not understand the usefulness of it. The boy calls him the chief. The old man is standing on a crane, and tries to persuade the kid to not become a pirate since it would ruin the town's reputation. He insists that despite the fact that the captain looks like a reasonable person, Luffy should not hang around him anymore.
Later, the doors at the Partys Bar are fixed. The boy and Makino are staying there alone, while the bartender is cleaning a glass. Makino mentions that the pirates have been out for a while and asks him if he misses them. Luffy replies that he does not because he has not forgiven them for the bandit incident yet. As the boy is playing with a glass that only contains a few cubes of ice, he claims that he overestimated Shanks. Luffy thought that the red-haired man was a tough pirate, so he is disappointed. Makino thinks that people that can stand up after getting picked on are brave. The boy tells her that she does not understand, since there are times when men must fight back, so the bartender confirms that she does not understand, and Luffy affirms again. Suddenly, a man enters the bar and excuses himself. Luffy is surprised, the man is revealed to be Higuma and he enters the bar along with his group of bandits. He observes that the pirates are not there, so the bar is quiet. The entire group sit at the tables, while the boy and the girl keep looking at them. The bandit leader asks her what is she waiting for, saying that there are customers and orders her to bring them sake.
Soon afterward, Makino rushes through the village to find the Mayor because Luffy has gotten himself into a hostage situation with Higuma after the bandit said something that angered him. As Makino and the Mayor return to reason with the bandit, the bandit states that it is already too late because Luffy is going to die. As Higuma raises his sword to kill Luffy, Shanks and his crew reappear. Higuma and his men tell them that it is none of their business.
As Shanks walks forward, one of the bandits points a gun at Shanks, only to be shot by Lucky Roux. Shanks tells Higuma that he will not allow him to hurt a friend of his and get away with it. Higuma, unfazed by his speech, sends the rest of the crew after him. Beckman decides to step in and single-handedly takes out the entire gang of bandits, leaving Higuma alone. Realizing he cannot win, Higuma drops a smoke bomb and takes Luffy away. As the smoke clears, Shanks realizes Luffy is gone and panics.
Out at sea, Higuma and Luffy stand in a boat. Higuma decides it is time to lose Luffy and kicks him into the water. Angry that he could not do anything to Higuma, Luffy struggles in the water as a Sea King appears. The Sea King eats Higuma, who is unable to do anything to defend himself, before turning toward Luffy. Moments before Luffy is eaten, Shanks saves his life and scares away the Sea King with a stare. When the Sea King is gone, Luffy begins crying upon realizing Shanks has lost his left arm in saving his life.
Finally, Luffy realizes he is too young to sail out to sea and become a pirate, as well as what a great man Shanks is. Later at the docks, Luffy says goodbye to Shanks and his crew and admits he is sad that they are leaving, but is not worried about going with them because he has decided he will become a pirate on his own. This leads to Shanks stating that he did not want him on his crew in the first place before claiming that there is no way Luffy can become a pirate. Luffy angrily proclaims he will become a pirate, gather a crew strong enough to beat Shanks', find the world's greatest treasure, and become the Pirate King no matter what. Happy about Luffy's decision, Shanks gives him his straw hat and tells Luffy to give it back when he has become a great pirate. Honored by Shanks's gesture, Luffy cries. As Shanks boards his ship to leave, Beckman comments on how Luffy will become big. Shanks admits that he knows Luffy will because he reminds him of himself when he was young.
Ten years later, Luffy leaves the village to start his own pirate crew and begin the journey of becoming the Pirate King.