The Mermaid and starfish, named Keimi and Paggag, respectively, thank the Straw Hats for helping them, and Keimi offers to give them some Takoyaki (fried octopus), after she meets up with her friend Hacchin as thanks. However, a call from him reveals that he has been kidnapped by the Fishman Macro Gang as bait for her. Luffy decides to rescue him for the Takoyaki, and the crew sets sail for their hideout. En route, they're briefly attacked by the Flying Fish Riders, a gang of ruffians aiding the Macro Gang, who are commanded by a masked man named Duval.
After reading an account of the various adventures that the Straw Hats have had, Brook resolves to be as much use as he can to prove his worth, but his well-intentioned efforts only manage to annoy or get in the way of the others. Brook then reveals his insecurites to Robin, saying that he'll leave the crew if he proves to be only a burden. Robin tells him that she used to feel similarly, until the Straw Hats came to save her at Enies Lobby, and she had finally found her place. Encouraged, Brook later reflects on how he has found his place after decades of being alone, and resolves to do his best so that he can have stories to tell of his own.
After traversing the treacherous Serpent Currents, the Straw Hats finally arrive at the Red Line, signifying that they've sailed halfway around the world and that their voyage is half over. While the crew reflects and takes a well-deserved rest, a sea monster attacks. Luffy easily dispatches it, forcing it to spit up a talking starfish and a genuine Mermaid onto the Sunny's deck.
Duval bears a grudge against one of the Straw Hats, but it is not known which one. When the Straw Hats reach the hideout, they discover that Hacchin is none other than the octopus Fishman Hatchan, formerly of Arlong's crew. Although reluctant to save him with this new knowledge, Keimi convinces the crew to go through with it. However, everything was a trap set by Duval, and the Straw Hats are ambushed by the Flying Fish Riders.
While the battle between the Straw Hats and the Flying Fish Riders rages on, Zoro frees Hatchan from his cage, and the Fishman in turn saves him from an attack, revealing that he feels bad about their battle at Arlong Park. Meanwhile, Luffy crashes into Duval's hut and catches a glimpse of his unmasked face before being chased back outside. Once outside, Duval reveals that Sanji is the Straw Hat he wants to kill. After Luffy knocks his helmet off, the reason for his hatred is laid bare: Marines and bounty hunters have been relentlessly pursuing him because he looks exactly like the poorly-drawn visage on Sanji's wanted poster!