Zoro arrived in Shells Town during his journey, where Helmeppo, the spoiled son of the crooked Marine captain Axe-Hand Morgan, released his pet wolf in the area. It tried to attack a girl named Rika, but by destroying it, Zoro rescued her. It is assumed that Helmeppo told Zoro to agree to be bound to a pole for a month to obtain amnesty based on Rika's account, which would maintain his integrity in Marine's eyes.
Koby and Luffy arrived in town on the ninth day of Zoro's restraint, with Koby's plans to join the Marines, and Luffy invited Zoro to be his first crewmember. Finally, in time to see Rika attempting to feed him some rice balls that Zoro declined, they arrived where Zoro was being kept, most likely to prevent the girl being captured as there was a sign forbidding anyone to help Zoro. Helmeppo ended up stomping the food badly because it was sweet while the rice ball was meant to be salty. Luffy asked Zoro to join him after they left, but he flatly declined to become a pirate. Luffy was then asked to feed him the dirty rice balls and to tell Rika that the food was delicious, revealing his goodness. Rika demonstrated to Luffy and Koby later in town the explanation for the capture of Zoro, which only confirmed Luffy's decision to have him as his crewman. When Helmeppo said he would execute Zoro in three days, Luffy punched him violently for breaching his vow, which send Helmeppo scurrying to his father, seeking revenge.
Luffy went to the Marine Base with the expectation that if he got Zoro his swords back, Zoro would join his crew. Luffy caught the wrath of Morgan by smashing his new-built statue and forced Helmeppo to show him where the swords of Zoro were. Meanwhile when attempting to untie him, Koby explained to Zoro the situation. Just in time, Luffy returned to rescue them from a firing squad. Refusing to die, Zoro accepted an invitation from Luffy and unveiled his unusual style of fighting. He also revealed that Luffy embraced his dream of being the best swordsman in the world, claiming that the Pirate King should have the best in his crew. Then Luffy went on to fight with Morgan. When Helmeppo tried to kill Koby, however, Luffy knocked him out while the captain was defeated by Zoro.
Seeing their tyrant leader defeated at last the Marines rejoiced and allowed Luffy and Zoro to go free. The Marines, however, ordered them to leave the island because they were pirates, but vowed not to report them to the headquarters. Officer Ripper asked about Koby's history when they were leaving. To help Koby cover it he was provoked by Luffy to start a short fight between them. Before it could get too serious, Zoro stopped the battle, but it was enough for Koby to gather the courage to ask Ripper if he could join the Marines, to whom Ripper gave permission. Upon leaving, Luffy and Zoro were saluted by Koby and the Marines for their efforts. Then Luffy and Zoro drove to their next stop.