"Precure All Stars New Stage: Mirai no Tomodachi" is a crossover film that brings together the Pretty Cure teams from various seasons, including "Smile Precure!," "Suite Precure♪," and "HeartCatch Precure!," alongside earlier generations. The story centers on the appearance of a mysterious girl named Fuu, who is revealed to be a fairy from the Land of Songs. Fuu seeks the help of the Precure teams to protect her world from a dark force known as Fusion, which threatens to consume both the Land of Songs and the human world.

Fusion is a malevolent entity that feeds on negative emotions, growing stronger as it spreads despair. It manifests through shadowy creatures called Negatones, which attack the Precure teams and drain their energy. The Precure must unite to combat this threat, but their efforts are complicated by the emergence of a new antagonist, Evil King, who seeks to exploit Fusion's power for his own ambitions. Evil King manipulates Fuu's insecurities, leading her to doubt her worth and question her ability to protect her world.

As the story progresses, the Precure teams confront their own vulnerabilities and fears, emphasizing the importance of friendship and trust in overcoming adversity. Fuu's character arc is central to the narrative, as she learns to believe in herself and her bond with the Precure. The climax features a large-scale battle against Fusion and Evil King, with all the Precure teams combining their powers to create a unified attack. This collective effort highlights the theme of solidarity and the strength that comes from working together.

The film also introduces a new Precure, Cure Echo, who plays a pivotal role in the final confrontation. Cure Echo's transformation and abilities are tied to the power of hope and the connections between the Precure teams. The resolution sees the defeat of Fusion and Evil King, restoring peace to both the Land of Songs and the human world. Fuu's growth as a character and the reaffirmation of the Precure's unwavering friendship serve as the emotional core of the story, reinforcing the series' recurring themes of courage, unity, and the enduring power of hope.