In an alternate timeline, Smart Brain has achieved world domination, and Orphnochs outnumber humans who have been driven to near-extinction. Takumi Inui, the bearer of the Faiz Gear, was once hailed as mankind’s savior until a brutal Riotroopers assault left him missing and presumed dead. His ally, Mari Sonoda, has formed a tireless human resistance that strikes Smart Brain’s headquarters in hopes of seizing the top-secret Emperor Belts, but the plan repeatedly falls short. The trio of Orphnochs—Yuji Kiba, Naoya Kaido, and Yuka Osada—dream of a coexistence between Orphnochs and humans, yet their peaceful vision clashes with a fearful populace. At the heart of Smart Brain’s machine, the chief, Kyoji Murakami (now reduced to a head in a water tank), insists that humanity’s time is over and hints at the Emperor Belts, introducing the powerful weapon bearer Leo who can transform into the formidable Kamen Rider Psyga.
Meanwhile, in a beleaguered human refuge called Paradise, Takumi lives under an alternate alias, Takeshi, working as a cobbler and sharing a home with a girl named Mina. When Yuji, Naoya, and Yuka warn that Psyga’s power is upon them, Paradise is suddenly invaded by Riotroopers. Masato Kusaka, as Kaixa, confronts Psyga but is swiftly defeated. Psyga aims to claim the Kaixa Belt, yet he is repelled by the alliance of three Orphnochs and their human allies. That evening, Takeshi and Mari cross paths at a masquerade, but Riotroopers crash the party, prompting Takumi to regain his memories and resume his Faiz identity—rejoining Auto Vajin to repel the attackers. The frictions deepen as Mari’s rumors about Takumi’s “savior” past alienate him, and some resistance members grow suspicious that Takumi might be an Orphnoch himself due to his Faiz-enhanced abilities. Mina reveals a troubling truth: years earlier, her father saved Takumi after a Riotrooper attack and implanted false memories to protect him. After Mina is fatally shot by Mizuhara, a resistance member who steals the Faiz Belt, Yuji kills Mizuhara and retrieves the belt, but the resistance subsequently exiles Yuji, Naoya, and Yuka until they prove themselves worthy of joining the Emperor Belt mission.
The next day, the Orphnochs press Smart Brain HQ, where Murakami unleashes the colossal Elasmotherium Orphnoch. Yuka dies in the onslaught, and Naoya is devoured, while Smart Lady deceives Yuji into thinking Mari betrayed them. In Paradise, a serum devised by Professor Nomura enables Keitaro Kikuchi to transform into Kaixa and briefly save Mari, though the Kaixa Belt soon dissolves into dust. Psyga abducts Mari, sowing discord within the resistance, while Takumi races to Tokyo to rescue her. In the Smart Brain Super Arena, Mari is destined to be fed to the Elasmotherium Orphnoch before a worldwide audience, but Takumi interrupts the event, transforming into Faiz to confront the behemoth. Auto Vajin is destroyed, and Faiz faces overwhelming odds when Psyga interferes. The Elasmotherium Orphnoch is restrained to prevent stadium devastation, and Faiz finally defeats Psyga by severing him with the Faiz Edge. Yuji Kiba arrives in the arena wearing a second Emperor Belt and becomes [Orga], altering the balance of power. Orga battles Takumi, forcing him out of Faiz before both fighters revert to their Rider forms while Mari is captured once more to be fed to the monster. Faiz, in Blaster Form, defeats Orga, but the night’s toll continues as a dying Yuji urges Takumi to pursue a lasting peace between humans and Orphnochs. Murakami’s severed head is crushed in a blunt denouement, and under a somber sky, Takumi and Mari walk away together, vowing to seek a place where they can live freely.
