Ryunosuke Momose [Akiyoshi Nakao] lives in a ruined, 2071 world where demons dominate and humanity is enslaved. An elderly inventor named George Karizaki [Noritaka Hamao] reaches out to him with a critical mission: using a Cyclotron Driver to send his consciousness back to 2021 so he can alter the timeline and save the future by becoming Kamen Rider Century. To pull this off, Ryunosuke must team up with his father from that era, Hideo Momose [Arata Furuta], and together they must navigate a perilous path through time and memory to set the planet right.
In 2021, a resurgent threat awakens the demon Diablo [Yoji Ueda], who is joined by the Deadmans and their allies, the Crispers, who revere him as kin. As these dangers simmer, Ikki Igarashi [Kentaro Maeda] finds himself at Happy Spa, reconnecting with old allies—Mei Sudo [Asuka Kawazu], Ryo Ogami [Yuki Ikushima], and Sora Ogami—while witnessing a tense confrontation between Hideo Momose [Arata Furuta] and his son Shinichi. The moment becomes a catalyst, pushing Ikki to intervene and uncover a larger conspiracy rooted in the past.
George Karizaki [Noritaka Hamao] becomes aware of the escalating threat when Himiko Crisper [Rica Matsumoto] attacks Reika Shindai and Ryoga Shindai at the Southern Base. To investigate, he sends Daiji Igarashi [Wataru Hyuga] to scout a location and verify his suspicions. Meanwhile, Rintaro Shindo [Takaya Yamaguchi] travels to the Northern Base at the behest of Sophia [Rina Chinen] to return the Kaenken Rekka to Touma Kamiyama [Shuichiro Naito], another thread in the tangled web of Rider legacies.
The story intensifies when Ryunosuke arrives from the future to help, but his contact with the world remains impossible. Diablo attacks, and Ikki, together with his inner demon Vice, transforms to face the threat. Ryunosuke urges Hideo to transform into Kamen Rider Century alongside him, yet their fusion spirals into instability, culminating in Century Break. The crisis forces Ikki and Vice to seek help from Touma and Rintaro to stabilize the father and son and restore their humanity.
George, now deeply invested in the unfolding events, explains that Diablo’s seal traces back to a Shocker laboratory, with the evil being sealed away and later released by scheme and theft. The stakes rise when a singularity in Egypt signals further trouble, prompting Yuri to dispatch Ryo Ogami [Yuki Ikushima] and Tetsuo Daishinji [Hiroaki Oka] to confront the Khufu Crisper, highlighting the global reach of the conflict. The revelation that Ryunosuke time-traveled from the past to the present throws himself and Hideo into a painful reckoning about family, responsibility, and the heavy cost of salvation.
Ryunosuke finally clarifies his own timeline: he was a 1971 geneticist whose work was branded “demonic” by Shocker, a past that landed him in the agency’s dark projects. He helped engineer captured humans into Kaijin, including Takeshi Hongo, the first Kamen Rider. When Takeshi urged him to embrace science for good, Ryunosuke attempted an escape but was captured and used as the first test subject for Diablo. Diablo’s rampage carried him into a drift through a wormhole that eventually delivered Ryunosuke to 2071, where he met George and gained the means to travel through time.
With the truth laid bare, Ikki persuades Ryunosuke to pursue a proper reconciliation with Hideo. Yet Ryunosuke’s physical body in 2071 remains in danger, forcing a grand plan: a multinational guard to shield his future body while several squads fight across the globe. The mission relies on the Book Gate Wonder Ride Books and a future-powered clone Rider system, enabling a coordinated assault against the Crispers. The team includes Kento Fukamiya [Ryou Aoki], Ren Akamichi [Eiji Togashi], Ryo Ogami [Yuki Ikushima], Reika Shindai [Angela Mei], Ryoga Shindai [Ken Shonozaki], and Hiromi Kadota [Junya Komatsu], while Touma Kamiyama [Shuichiro Naito], Yuri [Tomohiro Ichikawa], and Sakura Igarashi [Ayaka Imoto] coordinate critical roles from the field.
As the plan unfolds, the fight broadens to include the deeper Rider lineage: Ikki Igarashi [Kentaro Maeda] as Revi, and the broader roster of Riders who meld into a united front—Sophia [Rina Chinen] as Calibur, and Reika Shindai [Angela Mei] as Sabela, among others. The longer arc centers on the revelation that Century was created specifically to confront Diablo, a truth that reshapes every ally’s purpose. The teams work in tandem, with Touma’s ascent to Xross Saber and Revice’s Neo Batta Genome upgrade signaling a bridge between generations of Riders as they combine their powers.
The climactic battle culminates in a coordinated strike that leverages the strengths of every rider and each Rider Kick, designed to cancel Diablo’s ritual once and for all. As victory finally nears, Diablo is defeated, but not without a price: Ryunosuke begins to fade from existence. In a poignant farewell, Takeshi Hongo’s spirit visits Ryunosuke, thanking him for carrying the Rider legacy forward. With Takeshi’s blessing, Ryunosuke vanishes, and Hideo rides the bullet train with Shinichi, clutching his father’s ticket as a quiet tribute to the long road they walked together. The future is saved, but the memory of the 50-year Rider lineage remains a beacon for those who continue to carry the legacy.
