Known as a Rogue Hero in the fantasy world Arezard, Akatsuki decided to take upon the request of the defeated Demon King to take his daughter with him. After bringing her back to the world he came from, Akatsuki brought her to join Babel, an academy-like organization that specializes in training those who came from the other world.

20 years after his escape from Impel Down, the legendary pirate Shiki, the Golden Lion, reappears causing massive upheaval to the Marines. During his long seclusion, he was able to come up with a scheme to bring the World Government to his knees. On his way to execute the plan, Shiki crosses paths with the Straw Hat Pirates and becomes so impressed with Nami's knowledge of meteorology that he abducts her to forcedly enlist her into his crew. Luffy and the gang end up on a strange land populated with monstrous beasts as they desperately search for Shiki and Nami.