Two years after the Paramount War, each member of the Straw Hats returns to Sabaody Archipelago. However, a group calling itself the Straw Hats is having everything their way and is recruiting new members.

The Straw Hats finally set up a plan to leave Sabaody Archipelago, while the fake Luffy tries to punish those who insulted him. Things get even more chaotic when the Navy raids both Brook's concert and the gathering of the fake Straw Hats.

The Straw Hats finally reunite after two years; with the help of all their supporters, they set sail for Fish-Man Island; while admiring the underwater scenery, Franky tells the story of a man who protected the Sunny.

With Caribou and his crew hot on their tail, the Straw Hats descend to the depths of the sea to get to Fish-Man Island.

The crew plumb the depths of the sea in search of Luffy, Sanji and Zoro; they encounter the terrifying and mysterious secrets of the deep, including an undersea volcano.

The Straw Hats finally land on Fish-Man Island, but they get separated. Luffy, Usopp, Sanji, and Chopper reunite with Camie and she leads them to the Mermaid Inlet where Sanji's "enthusiasm" gets them into trouble!