The protagonist is a modern young man who travels to the world of the anime One Piece. Through his soul, he becomes Neptune, the king of Fish-Man Island. He also gets a system. Every time he changes the plot, there is a reward. The greater the change, the greater the reward. Not only does he change the fate of his princess Otohime being killed, but also changes the entire Fish-Man Island, unifying the entire One Piece world through the fish-men of Fish-Man Island.
