The narrative centers on a reality-bending crisis orchestrated by Tid, a powerful Super Time Jacker who seeks to erase the legacy of all Heisei Kamen Riders. Tid targets a young boy named Shingo, whose unique existence serves as the anchor connecting the modern Heisei era with the legendary heroes of the past. As Tid alters history, Kamen Rider Build, Sougo Tokiwa (Kamen Rider Zi-O), and their respective allies notice catastrophic changes in their timelines, including the sudden disappearance of Rider history from public
consciousness and the erasure of memories.Driven by an unwavering sense of justice and a desperate need to protect children from losing their heroes, Sougo and Sento Kiryu forge an alliance. They soon discover that Tid is manipulating both time and space to fuse worlds together, weaponizing powerful Mirror Monsters and corrupted Imagins against them. The stakes escalate dramatically when the duo encounters Ataru, an older youth who has lost his childhood belief in Kamen Riders, viewing them as mere television fiction. Ataru’s skepticism makes Shingo vulnerable, as the bond between children and their idols fuels the very existence of the Riders.Through a series of intense, high-octane battles across various temporal dimensions, Sougo and Sento manage to reach Ataru. Moved by the fierce
determination of the Riders who refuse to yield despite being forgotten, Ataru rekindles his lost memories and embraces his inner child. This pivotal emotional breakthrough restores the connection between Shingo and the legacy of the Heisei era, sending a massive surge of hope-fueled energy across time.With history realigned and the collective might of the Heisei Riders restored, a monumental final showdown erupts against Tid and his monstrous army. Every main Heisei Kamen Rider—from Kuuga to Build—materializes in a breathtaking display of unity, combining their ultimate powers to overwhelm the villain. In the climactic clash, Zi-O and Build deliver devastating finisher attacks that obliterate Tid once and for all, shattering the temporal anomaly he created.As peace is finally restored to the multiverse, the timeline stabilizes. Shingo and Ataru are reunited with their memories intact, fully cognizant of the eternal guardians who watch over humanity from the shadows. The Heisei Riders part ways, fading into the sunset with the quiet assurance that their legacy of courage, sacrifice, and justice will forever live on in the hearts of the people they protected, marking a triumphant celebration of an entire era of heroes.