"Guyver: The Bioboosted Armor" centers on Sho Fukamachi, a high school student who stumbles upon a mysterious alien device known as the Guyver Unit. Upon activation, the unit fuses with Sho, transforming him into a biomechanical warrior called the Guyver. This symbiotic armor grants him immense strength, speed, and regenerative abilities, but also draws the attention of the Chronos Corporation, a powerful organization secretly controlled by an alien race called the Zoanoids. Chronos seeks to reclaim the Guyver Unit to further their plans for global domination.

The Zoanoids are genetically engineered creatures created by Chronos to serve as soldiers. They can disguise themselves as humans, making them a pervasive threat. Sho, now a target, is forced to confront these creatures while grappling with the moral and physical challenges of his newfound power. Along the way, he allies with Mizuki Segawa, his childhood friend, and Tetsuro Segawa, her younger brother, who provide emotional support and assistance. Another key figure is Agito Makishima, a mysterious and skilled fighter who harbors his own agenda against Chronos.

As the story progresses, Sho uncovers the origins of the Guyver Units, which were created by an ancient alien civilization to combat the Zoanoids. Chronos, led by the enigmatic Dr. Balcus and his superior, Archanfel, seeks to harness the Guyver's power to perfect their Zoanoid army. Sho's battles escalate in scale and intensity, culminating in confrontations with high-ranking Zoanoids and other Guyver users, including Guyver III, a rival unit controlled by a rogue Chronos operative.

The narrative explores themes of identity, power, and the consequences of technological advancement. Sho's journey is marked by personal growth as he learns to balance his humanity with the destructive potential of the Guyver armor. The series combines action, science fiction, and horror elements, with a focus on the conflict between Sho and the ever-expanding forces of Chronos. The story builds toward a climactic struggle for survival, as Sho and his allies fight to prevent Chronos from achieving their ultimate goal of subjugating humanity.