Misaka Mikoto, a young girl from Tokiwadai Middle school and one of the seven LEVEL 5 of Academy City find herself in the World of One Piece at the time Gol D. Roger was alive, she meet WhiteBeard and Roger and decide to join him in his last journey, after return at Academy City Misaka's adventure with Roger inspired her to become a Pirate and return to Grandline with her friends.

After arrival in Gamindustri and freeing Nepgear and Blanc from ASIC, Kazuma who is Blanc's lover learn about what happened to the world after she left, determinate to protect the world his family saved years ago, Kazuma, Blanc & Nepgear embark on a journey to seek the Mascots & saving Gamindustri, unknown to them enemies from Kazuma's world also appear with bad intentions