Chapter 591 is titled "You Sure That's Alright?".
The Heart Pirates spot someone killing a Sea King, who then swims to the shore near the Heart Pirate's location. The person revealed himself to be Rayleigh, much to their surprise, and even more so when he makes it known that he knows Luffy is on the island too. Hancock, along with her sisters and Nyon, come to bring Luffy food just as Luffy and Jinbe meet up with Rayleigh. The two also notice that the Heart Pirates have left which Rayleigh confirms, telling Luffy that Law said to take it easy for two more weeks. Hancock's group soon arrives at Luffy's location. Nyon is surprised to see Rayleigh. It is then revealed that Elder Nyon and the Gorgon Sisters are friends with Rayleigh and Shakky. When Jinbe sees the food, Hancock glares at him, saying that the food was meant only for Luffy, but then allowed him to take only a little. Luffy and Jinbe begin to eat. Rayleigh delivers a letter to the Boa Sisters from Shakky. Rayleigh also mentions that he figured out Luffy's location thanks to Kuma after the battle on Sabaody and also to Shakky's intuition after the Marineford War.
Rayleigh then asks Luffy if he plans on returning to Sabaody, which Luffy confirms. However, Rayleigh mentions that if they go back, the whole incident could start all over again. He then says he has a plan and it is up to Luffy if he wants to go along with it.
We then shift to island Greenstone in the Boin Archipelago, where Usopp, now fat from eating the island's natural food, is trying to fight his way past a giant horned beetle despite the pleas of his companion, Heracles. He gets knocked down and Heracles mentions that the further out from the center of the island he goes, the tougher the creatures are, making it impossible to escape. Usopp does not listen though and takes off again just as Sea Kings, distracted by the smell of the island, start coming in. Heracles notices the island beginning to move and warns Usopp to cling to something as we find out the island is actually a large carnivorous plant called the Stomach Baron. Usopp is nearly eaten but Heracles saves him and asks what is wrong, having noticed that Usopp's mood had changed since reading a newspaper that a news coo dropped earlier. Usopp answers that he found out about Ace's death and is trying desperately to get off the island to help Luffy through his pain. Otherwise, he could not call himself a member of the Straw Hats.
Meanwhile, in the Torino Kingdom, Chopper is all set to leave, having helped the natives and the birds of the island get along. It turns out the reason the birds attacked the natives was because they thought they were stealing their eggs. In actuality, the natives just wanted the plants near their trees. Chopper also found out about what happened to Ace and wished to get off the island to treat Luffy's wounds. Bidding the island's residents farewell, Chopper heads off on one of the birds. They pass a News Ku and Chopper grabs a paper from it. He finds something about Luffy in the paper and begins to panic.
- Silvers Rayleigh is the first seen person to be able to cross the Calm Belt by swimming.
- The Heart Pirates leave Amazon Lily.
- Luffy regains his hat.
- It is revealed that Elder Nyon and the Gorgon Sisters have a history with Silvers Rayleigh and Shakky.
- The message that Kuma gave to Rayleigh is revealed.
- Rayleigh decides to help Luffy with a plan of his.
- Usopp and Chopper are seen again wanting to reunite with Luffy.
- Chopper ends the conflict between the natives and the giant birds.