Kamen Rider Build the Movie: Be the One

Lore & Background

The film follows the aftermath of a civil war in Japan, where new city-state governors promise prosperity. However, Touto governor Kengo Inō rallies anti-Kamen Rider sentiment by hypnotizing the populace into seeing Sento Kiryū as an enemy. Sento, as Kamen Rider Build, is chased by a mob after saving a boy and his sister. Kazumi Sawatari and Gentoku Himuro help him escape but are captured by Hokuto governor Ryōka Saiga, who appears as the Scissors Lost Smash. Sento later learns that the three governors are members of the Blood Race, like Evolt, and have been manipulating events to destroy Earth. They brainwash Ryūga Banjō into attacking Sento as Kamen Rider Cross-Z, and Inō uses the Hazard Trigger and other items to become Kamen Rider Blood.

Reader's Guide

The film is significant as a direct continuation of the Kamen Rider Build television series, filling a narrative gap between episodes 45 and 46. It introduces the concept of the Blood Race as the true antagonists behind the series' conflicts and features the debut of Kamen Rider Zi-O, the protagonist of the next Kamen Rider series. The film's plot explores themes of public perception of heroes and the manipulation of memory, as the populace is hypnotized to view Kamen Riders as symbols of civil war horrors. The climactic battle sees Sento and Ryūga merge into Kamen Rider Cross-ZBuild, a combined form that defeats the Blood Race members. The film also sets up future storylines, with Sento researching how to replicate the Cross-ZBuild combination to defeat Evolt. Despite competition from major releases like Mission: Impossible – Fallout and Incredibles 2, the film grossed $4.8 million at the box office.

Did You Know?

• The film was initially planned to be a zombie film but was changed to avoid being seen as a horror film.
• All three members of the Blood Tribe were originally intended to become Kamen Riders, but budget constraints limited this to only the leader.
• The film was released in a double billing with Kaitou Sentai Lupinranger VS Keisatsu Sentai Patranger en Film.

Narrative Placement and the Fall of the New Order

This theatrical feature slots directly between the forty-fifth and forty-sixth installments of the television run, functioning as a pivotal interlude in the ongoing saga. The story opens in the fragile aftermath of the civil war, where the freshly inaugurated city-state governors of Touto, Hokuto, and Seito project an image of renewed national prosperity. That veneer shatters almost immediately when Touto's governor, Kengo Inō, manipulates the hypnotized citizenry into viewing Sento Kiryū as a domestic threat. What follows is a relentless pursuit through the streets, with Sento rescuing a young boy and his sister before his allies Kazumi Sawatari and Gentoku Himuro sacrifice their freedom to cover his escape, captured and weaponized as the Scissors Lost Smash. The narrative then escalates as Sento tracks down the abducted Ryūga Banjō, only to discover that Seito's governor Mitsuomi Gōbara has transformed into the Zebra Lost Smash and openly confesses to the death of Kasumi Ogura. The confrontation is cut short when Inō arrives and Gōbara infects a distracted Ryūga, setting the stage for the film's central crisis.

The Blood Race Conspiracy and the Build Annihilation Plan

Beneath the political theater of the new government lies a far darker truth. When Sento infiltrates a government database, he uncovers that the three governors are no strangers to one another; they were fellow members of Soichi Isurugi's Kiwami Project. Inō then lays bare the full scope of their treachery: all three are members of the Blood Race, the same alien lineage as Evolt, and they have been operating as his co-conspirators, quietly steering events toward the annihilation of Earth. Evolt's own deviation from their shared blueprint forced the governors to accelerate their timeline, launching what they call the Build Annihilation Plan. Central to this scheme is the brainwashed Ryūga, compelled to assault Sento in the form of Kamen Rider Cross-Z. After Build's defeat, Inō delivers a chilling justification, arguing that the populace genuinely perceives Kamen Riders as living reminders of the civil war's devastation rather than heroes. The plan culminates in Inō absorbing his fellow Blood Race members along with Ryūga into the monstrous Kamen Rider Blood, while Evolto drags the unconscious Sento into the unknown.

The Cross-ZBuild Fusion and the Final Stand

The film's emotional and action climax hinges on an unprecedented transformation. After a metaphysical confrontation with Takumi Katsuragi's lingering consciousness, in which Sento wrestles with whether Project Build truly honored his father's legacy, he returns the next day to deliver the Pandora Box to the governors. Inō reneges on their bargain, and Sento, now in Build Genius form, fights a losing battle before using the Gold Rabbit Fullbottle to pry Ryūga free from Kamen Rider Blood. With Utsumi freeing the captured allies and Vernage restoring Misora and Sawa, the stage is set for the ultimate combination. Vernage fuses the Silver Dragon and Gold Rabbit Fullbottles with the Genius Fullbottle to create the Cross-ZBuild Can, and Sento is inadvertently merged with Ryūga into the singular rider Cross-ZBuild. This hybrid form drives Blood back to the surface while Grease and Rouge dismantle the remaining Lost Smash threats. Once the Can reverts to its components, the group grapples with the fact that anti-Kamen Rider sentiment persists, yet Sento finds peace in the gratitude of the boy he saved.

The Bridge to Kamen Rider Zi-O

Beyond its role as a standalone theatrical chapter, the film carries enormous franchise significance as the narrative gateway to the next era of the Kamen Rider franchise. In its final sequence, Sento is deep in research, attempting to replicate the Cross-ZBuild combination as a strategy against Evolt. His work is interrupted when a white Pandora panel materializes and teleports him into a chaotic battlefield where multiple Kamen Riders are locked in combat with their respective adversaries. The tide turns when an enigmatic rider, equipped with the distinctive Build Armor, obliterates the remaining monsters and approaches Sento. This figure introduces himself as Kamen Rider Zi-O, the titular protagonist of the upcoming series, effectively making this film the official debut appearance of that character in the broader Kamen Rider universe. The encounter reframes the Build saga as one thread in a much larger tapestry of riders spanning time, and positions Sento's story as a foundational chapter for the Zi-O narrative that follows.