As a child, Uta—the Red Hair Pirates' ex-musician and Monkey D. Luffy's childhood friend—promised that she would build a new era of freedom by performing joyful music for the world.

Luffy and the Straw Hat Crew arrive at Uta's first ever live concert, where many fans have gathered to enjoy the diva's otherworldly singing. Due to a childhood trauma, Uta bears a deep-seated hatred for pirates; her happy reunion with Luffy is cut short when she learns that he has since become one. Luffy's refusal to change his ways results in Uta unleashing her powers on the Straw Hats. The crew soon learns that their minds have already been trapped in Uta's dream world since the beginning of the concert, while their unconscious bodies remain asleep in the real world.

With time quickly running out, the Straw Hats must find a way to escape the nightmare or be trapped in Uta's dream forever.