The episode cleverly links his identity crisis to the transformation system. To become Build, he must twist the Rabbit and Tank FullBottles together—two incompatible objects (speed vs. armor) forced to coexist. That is Sento: a gentle musician and a ruthless physicist, a victim and a weapon.
Following the more light-hearted Kamen Rider Ex-Aid , Episode 1 of Kamen Rider Build (2017) arrives as a cold, calculated reset. Within its first five minutes, the show establishes a tone of paranoia, mystery, and science-fiction body horror. The title, “They Are the Best Match,” operates on three levels: the literal combination of FullBottles (Rabbit & Tank), the forced partnership between Sento Kiryu and Ryuga Banjo, and the volatile fusion of human will with alien technology (Pandora Box). This premiere is a masterclass in efficient world-building, introducing a fractured Japan, an amnesiac genius hero, and a transformation system that feels less like magic and more like a controlled explosion. Kamen Rider Build Tap 1
This stands in stark contrast to the Smash, which are pure, unthinking chaos. Faust’s goal, revealed via the mysterious Night Rogue, is to create the ultimate chaotic being. Build is the answer to that: controlled chaos. The episode cleverly links his identity crisis to
His arc in this episode is tragic: he escapes prison only to find Kasumi transformed into a Smash. In the climactic battle, he begs Sento to save her, but Sento cannot. The transformation is irreversible. Ryuga is forced to watch Sento destroy the monster wearing Kasumi’s face. This isn’t a triumphant first victory; it’s a funeral. Ryuga’s subsequent handshake with Sento (“I’ll fight with you to find Faust”) is not born of friendship, but of mutual desperation. He is the hot-blooded, emotional anchor to Sento’s cold logic. That is Sento: a gentle musician and a
This is a radical departure from typical Kamen Rider protagonists (who are usually energetic high schoolers or righteous cops). Sento is a man running from a past he can’t access, yet his body remembers—his hands instinctively perform complex chemistry, his eyes calculate angles for a Rider Kick. His catchphrase, “Let’s begin the experiment,” is a coping mechanism. Every fight, every transformation, is an attempt to reverse-engineer the mystery of who he is.
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