Sho Fukamachi is a 17-year-old second-year student at Narisawa High School. Black-haired and slim-framed, his ordinary teenage life centers on studies and unspoken feelings for his friend Mizuki Segawa. This existence shatters when he discovers the mysterious bio-mechanical Guyver Unit I near Lake Narisawa. Accidental contact forces the unit to bond with him, encasing him in symbiotic organic armor that grants extraordinary abilities. This transformation attracts the clandestine organization Chronos, which deploys genetically engineered Zoanoid monsters to retrieve the unit, forcing Sho into a defensive war for his survival and the safety of those close to him. Initially terrified by the Guyver's destructive power and the trauma of bonding, Sho rejects the armor. He discovers it remains irrevocably linked, resummoning automatically during threats. His primary motivation is protecting his friends and family, especially Mizuki Segawa, whom he loves intensely, and her brother Tetsuro Segawa, his closest confidant. This protective instinct clashes with his self-doubt and tendency to blame himself for endangering others through his Guyver connection. His struggles intensify when Chronos captures his father, Fumio Fukamachi, transforming him into the anti-Guyver Zoanoid Enzyme II. Their confrontation leaves Sho critically damaged, triggering the Guyver's autonomous "heroic safe mode." In this berserk state, the armor kills Enzyme II without Sho's conscious control. Realizing he killed his own father causes profound trauma; Sho suppresses the memory and temporarily loses the ability to transform. The Guyver Unit provides immense physical enhancements: superhuman strength, speed, durability, and flight via a gravity control orb. Key weapons include high-frequency vibration blades, a head-mounted laser, sonic emitters (Sonic Buster), gravity-manipulating Pressure Cannons, and the devastating chest-mounted Mega-Smasher particle beam cannon. A control medal embedded in the armor's forehead regulates the unit and stores Sho's genetic and memory data. This enables near-instantaneous regeneration from injuries and full bodily reconstruction if the control medal survives, rendering him functionally immortal. However, damage or destruction of the control medal causes the armor to consume its host. Sho dies multiple times. His first death occurs against Genzo Makishima, transformed into Zoanoid Enzyme, who removes his control medal, causing armor overload and body disintegration. The recovered control medal regenerates him. He dies again during a rescue attempt for his father at Chronos' Relic's Point facility when Enzyme II extracts part of his brain; he regenerates once more. A third death follows when Chronos founder Archanfel deflects his Mega-Smasher, atomizing his body. His consciousness persists within an alien Creator ship fragment, which reconstructs him using his bio-data. This reconstruction evolves Sho into Guyver Gigantic, significantly amplifying his power with additional gravity orbs, an electromagnetic barrier, and the hundred-times-more-potent Giga Smasher particle beam. Later, through sheer willpower, he evolves further into the towering Guyver Gigantic Exceed, gaining increased destructive capabilities including the Gravity Implosion attack. Sho's development revolves around accepting the Guyver's burden. Initially viewing it as a curse disrupting his normal life, traumatic events—especially his father's death and confrontations with foes like the renegade Zoanoid Aptom, who forces him to confront suppressed guilt—forge his resolve. He vows never to retreat from truth or responsibility again. After Chronos executes its global takeover (X-Day), openly ruling Earth and offering public Zoanoid transformation, Sho's fight expands from personal survival to rebellion for human freedom. His innate sensitivity and protective nature, once vulnerabilities, become core to his resilience and leadership against overwhelming forces.