The Hikari Studio lands in a strange new A.R. World, and as the team studies the landscape, Natsumi Hikari begins to sense that they might have slipped into Tsukasa Kadoya’s own home world. Tsukasa Kadoya, Masahiro Inoue as Kamen Rider Decade, is the first to notice a familiar mansion shown in the backdrop, and when the trio tracks the building down and pushes open the door, they meet a girl named Sayo Kadoya, who immediately identifies Tsukasa as her older brother. The moment is tempered by the arrival of Nobuhiko Tsukikage, a stern caretaker who confronts Tsukasa about abandoning his sister for so long, and the tension between past loyalties and present danger hangs in the air. The scene shifts as the Nine Worlds begin to fuse with the World of Decade, a crisis that accelerates when Tsukikage reveals a startling possibility: the strongest Kamen Rider ever imagined could decide the fate of all worlds through a climactic “Rider Battle.” With Tsukasa’s memories returning and a sense of responsibility rekindled, he grants Tsukikage the authority to set this plan in motion, and the countdown to a multiverse showdown begins.
Three days pass, and a brutal six-person tag team battle unfolds: Decade along with Kuuga and Diend face off against V3, BLACK, and Super-1. The duel quickly tilts in favor of Decade’s resilience, but Diend bolts, Kuuga is wounded, and Decade is left to shoulders the fight solo. His victory bleeds into a larger transformation as a castle rises from the stadium, pulling Yusuke Onodera and Natsumi into a throne room where they are greeted by the world’s rulers as Dai-Shocker’s new pawns. Eijiro Hikari, known as Doctor Shinigami, makes his grand entrance and salutes Tsukasa as a hero who’s returned, signaling that their schemes are aimed at global domination across the saved worlds. The manipulation becomes clear: Tsukikage and Sayo belong to Dai-Shocker in different guises, and their combined power—amplified by the Earth Stone—pulls Kuuga’s greatest form into the picture, threatening both Natsumi and Yusuke’s safety.
As danger closes in, Yusuke’s friend Narutaki steps in to intervene, rescuing Natsumi as they’re whisked through another conquered world. Daiki Kaito, disguised as a Dai-Shocker soldier, crosses paths with them, and Narutaki’s faith in cross-world travel grows into a plan: gather the Kamen Riders to mount a united defense against the invasion. Meanwhile, Tsukasa is forced into a confrontation with Jōji Yūki, a former Dai-Shocker ally who seeks revenge for his lost arm and the downfall of his faction. The encounter pushes Tsukasa toward a path of mercy and change, a realization that becomes critical when Yūki’s robotic limb allows Tsukasa to escape and transform into Riderman.
The effort to recruit other Riders encounters renewed resistance: an attempt to recruit Kamen Riders Ouja and Kick Hopper falls apart, leaving Diend and Natsumi to fend off a Dai-Shocker platoon led by General Jark. Diend’s resourcefulness with Raia, Gai, and Punch Hopper gives them a fighting chance, and Tsukasa arrives just in time to help drive Jark back to the castle’s edge. The siege continues as the castle’s gates open to reveal an army led by Doctor Shinigami and Ambassador Hell, with Ikadevil and Garagaranda under their command. One by one, the Riders fall in battle, until the rising, Bishium-controlled Rising Ultimate Kuuga descends to kill Decade. Sayo steps forward and, in a pivotal moment, pushes away the Stone of the Earth’s control, freeing Yusuke from its grasp as Shadow Moon moves in to finish the job.
But hope arrives in the form of Kamen Rider W, a dynamic duo composed of Shotaro Hidari and Masaki Suda as Philip. Their timely appearance helps turn the tide, and they take Shadow Moon out of the equation with a swift, decisive strike. The other Riders rally around Decade, and together they unleash an All Rider Kick that shatters the Dai-Shocker castle and shatters the threat to all the worlds. The blast also awakens a primal force: King Dark, who rises in the wake of the castle’s destruction. Diend then arrives with Kamen Rider J, and using the DecaDriver Final FormRide card, transforms Decade into Jumbo DecaDriver. J evolves into Decade Complete Form Jumbo Formation, delivering a Dimension Kick that finishes King Dark and closes the most perilous breach between the universes.
In the aftermath, Tsukasa seeks reconciliation with Sayo and vows to restore trust, but Sayo has found her own path and begins a new journey of her own. Tsukasa returns to the Hikari Studio—his real home—and finds a familiar figure, Eijiro, reappearing as if nothing happened, signaling that the bond between worlds is both broken and rebuilt, depending on where one places their faith and memory. The film closes on a note of renewed purpose and a sense that the journey of a single rider can ripple across countless worlds, reshaping destinies and redefining what it means to belong to a family, a faction, or a future.
- Renn Kiriyama as Shotaro Hidari and Masaki Suda as Philip, Kamen Rider W, make a high-spirited entrance that helps tilt battles toward unity.
- Masahiro Inoue as Tsukasa Kadoya / Kamen Rider Decade remains at the center as a conflicted yet determined figure whose choices ripple through the multiverse.
- Ryuichi Ohura as Nobuhiko Tsukikage / Shadow Moon and Gackt as Jōji Yūki provide some of the film’s most volatile confrontations and unexpected twists.
- Ren Osugi as Ambassador Hell and Renji Ishibashi as Doctor Shinigami anchor the Dai-Shocker leadership and its dark designs.
- Masaki Suda, Renn Kiriyama and the others weave together a sprawling, multiversal tapestry that pays off with emotional resolution and an all-out, celebratory clash of heroism.
