Kamen Rider Build The Movie: Be The One

Following the civil war, Touto's new city-state governors are sworn in and promise prosperity. Governor Kengo Inō immediately begins rallying anti-Kamen Rider sentiment, portraying Sento Kiryū as an enemy of the state. The crowd is hypnotized into viewing the Rider as a threat, setting the stage for renewed conflict.

Sento saves a boy and his sister, drawing the attention of a hostile crowd. A mob pursues Kamen Rider Build through a stadium as Kazumi Sawatari and Gentoku Himuro shield him before their capture. The escape demonstrates the depth of the governors' manipulation and the Rider's precarious position.

Misora and Sawa are subdued as Sento reaches Nascita, attempting to contact Ryūga Banjō who has been abducted. Mitsuomi Gōbara provokes a fight when Sento transforms into Zebra Lost Smash, revealing Ryūga's link to Kasumi Ogura's death. The confrontation deepens the conspiracy surrounding the new governors.

The clash peaks when Inō arrives on the scene while Gōbara infects Ryūga. The confrontation exposes the governors' direct intervention and the broader threat posed by the Blood Race. The battle sets the stage for a larger conspiracy to unfold.

Sento uses a government facility's database to confirm that the new governors are part of Soichi's Kiwami Project. Inō confronts him, revealing the broader conspiracy. The revelation shifts the conflict from personal battles to a planned act against Earth.

Inō explains the governors are Blood Race members who allied with Evolto to destroy Earth. They unveil the Build Annihilation Plan, and Ryūga, brainwashed, attacks Sento as Cross-Z. The moral and political stakes widen as the true mastermind's plan unfolds.

Build is defeated, and Inō reveals how the public now associates Kamen Riders with the war's horrors. Ryūga hands Sento his Hazard Trigger, and, with Blood's Fullbottle and his Great Cross-Z Dragon, becomes Kamen Rider Blood, absorbing kin as Evolto carries the unconscious Sento away. The escape marks a turning point in the saga.

Sento wakes in a safe place, recalling Takumi Katsuragi's memories of the Skywall Disaster. Evolto mocks him and explains Inō's need for the Pandora Box to destroy the world. Inō offers to trade Ryūga for the Pandora Box, pressing Sento into a desperate choice.

Sento debates Takumi in a metaphysical realm, lamenting past failures but reaffirming that Build protected friends. He argues that Ryūga is essential to Evolto's defeat, strengthening his resolve to push forward. The exchange deepens Sento's commitment to the mission.

Sento brings the Pandora Box to the governors, who back out of their promises. He accepts a fight to retrieve Ryūga, transforming into Build Genius. He uses the Gold Rabbit Fullbottle to extract Ryūga from Blood, rescuing him along with Blood's kin.

Blood combines the Hazard Trigger with the Pandora Box to attempt destroying the planet at its core. Kazumi and Gentoku battle Blood's kin after Nariaki Utsumi frees them, while Sento realizes Ryūga's Silver Dragon Fullbottle can cooperate with his own. The stakes rise to cosmic proportions as Earth hangs in the balance.

Vernage revives Misora and Sawa, merging their Fullbottles with Genius to form the Cross-ZBuild Can. Sento and Ryūga merge into Cross-ZBuild, forcing Blood back to the surface. Grease and Rouge eliminate Zebra and Scissors Lost Smash as Evolto's schemes crumble.

Even after Blood is defeated and the Cross-ZBuild Can is defused, anti-Kamen Rider sentiment remains. Sento remains undeterred, believing in a future built by those who can create change, especially after the boy he saved expresses gratitude.

Sometime later, Sento studies ways to reproduce Cross-ZBuild but is teleported by a white Pandora panel to a battle between various Kamen Riders and their enemies. A mysterious rider in Build Armor introduces himself as Kamen Rider Zi-O, signaling a new era and a looming crossover threat.