"One Piece Film Red" centers around Uta, a world-famous singer with a mysterious connection to the Straw Hat Pirates, particularly their captain, Monkey D. Luffy. Uta, who is revealed to be the adopted daughter of the legendary pirate Red-Haired Shanks, hosts a live concert on the island of Elegia, drawing massive crowds, including the Straw Hat crew. Her performances are powered by the Uta Uta no Mi, a Devil Fruit that allows her to transport her audience into a dreamlike world called Uta World, where their consciousnesses are trapped while their physical bodies remain in the real world.

As the concert unfolds, Uta's intentions become clearer. She seeks to create a utopia within Uta World, free from the chaos and suffering of the real world, but her plan inadvertently endangers the lives of those trapped in her dream. The Straw Hat Pirates, along with allies and enemies alike, must navigate the surreal and dangerous landscape of Uta World to uncover the truth behind Uta's powers and her connection to Shanks. The narrative explores themes of isolation, sacrifice, and the consequences of pursuing an idealized reality.

Key characters include Uta, whose tragic backstory and emotional struggles drive the plot; Luffy, who grapples with his bond to Uta and her ties to Shanks; and Shanks himself, whose presence looms large over the story as his past actions and relationship with Uta come to light. The film also features appearances by other prominent figures from the "One Piece" universe, including members of the Red-Haired Pirates and the World Government, adding layers of intrigue and conflict to the narrative.

The story builds toward a climactic confrontation as Uta's powers spiral out of control, threatening both the dream world and reality. The Straw Hat Pirates must work together to resolve the crisis, leading to a resolution that ties together the emotional and thematic threads of the film. "One Piece Film Red" blends action, music, and character-driven drama, offering a self-contained yet deeply connected entry in the "One Piece" franchise.