When does Franky join the crew?

Franky is standing on Scrap Island after chasing his undies to the Straw Hats' new ship through Water 7. He insists that Luffy, who is currently holding his swim trunks, give them back. He is slightly humiliated by the city's residents but still refuses to leave and even brazenly poses in front of the ship. Franky's tenacity impresses Luffy. Nami refers to Franky as a pervert, which is what the locals were calling him. However, Robin has an idea and requests permission to be rough with him. Robin grabs Franky's testicles with the help of the Dos Fleur Grab with Luffy's approval. He screams in agony and begins to flail around in pain. Franky is thrown to the ground. Luffy objects because he still wants Franky to be a man. In response, Robin advises the pirates to hold onto any loot they discover.

Franky keeps saying that he can't leave the island and he doesn't want to be a shipwright anymore; the Straw Hats' ship would be his last. At this time, Iceburg speaks up and recalls that Franky used to dream of building the perfect ship and sailing on it as its shipwright. He goes on to say that Franky's true motivation for staying put was to make up for Tom being taken to Enies Lobby for execution. Even though Tom and Iceburg have forgiven Franky, Iceburg insists that Franky must also ultimately accept forgiveness from himself. Iceburg tells Franky that it's time for him to start pursuing his aspirations once more as he breaks down in tears.

He receives a bag from the Franky Family, which has been pre-packed with his belongings. Zambai says that they were only trying to make him happy and that's why they made him run through Water 7 naked. He's still rolling around the debris piles in pain, but Robin has stopped squeezing his testicles by this point. She also claims that she just gave him one squeeze. He is crying for a different cause as he thinks back to how he gathered the rogues and the poor of the city, took them under his wing, and enlisted them to help defend Water 7. He is concerned about the well-being of his Franky Family, but the Franky Family claims that they would be alright and survive as they have learned a lot from their Big Brother.

Zoro and Sanji suddenly charge through the crowd and jump onto the ship. Zero warns that Vice Admiral Garp, Luffy's grandfather, has returned despite having earlier made a commitment to leave them alone. Luffy returns to Franky his undies. Once more emitting confidence, Franky claims that the Straw Hats are novices at ship maintenance and that a ship as magnificent as their new one would be in need of sympathy if it were not taken care of by an expert shipwright. Franky accepts their offer and joins their crew. Franky recalls Tom and the building of the Sea Train one last time, leaving the Franky Family and the Galley-La Company behind.

Franky chased his swim trunks to the Straw Hats' new ship, but he still didn't want to go with them, so Iceburg and Robin had to do some additional "convincing". While she tends to him, Zoro and Sanji learn that their time in Water 7 is running out since Vice Admiral Garp, Luffy’s grandfather, persued them.