Agito Makishima's life began with profound tragedy: his parents committed suicide after his uncle, Genzo Makishima, bankrupted their company. Genzo adopted Agito but offered no familial warmth, treating him solely as an employee within his own company, Max Pharmaceuticals. Following Max Pharmaceuticals' absorption by the powerful organization Chronos, Agito used his position as a management trainee to access Chronos secrets while secretly nurturing plans for revenge against Genzo and a future usurpation of Chronos itself. He masterminded the theft of three Guyver Units from Chronos. While Sho Fukamachi became Guyver I and Oswald Lisker became Guyver II, Agito secured and activated the third unit for himself. Maintaining absolute secrecy about this affiliation, he became Guyver III. Though he potentially activated his unit before Lisker, he remained covert until after Lisker's elimination, resulting in his designation as Guyver III. Agito operates as a strategic and ruthless anti-hero, consistently prioritizing his goals over sentiment. He views allies like Sho as pawns rather than equals. Demonstrating deep understanding of the Guyver's capabilities, he exhibits zero hesitation in endangering innocents if it serves his objectives. This cold pragmatism stems from his traumatic childhood and desire to ensure he is never powerless again. He harbors a belief in his inherent superiority over Sho, both personally and as a Guyver user. Initially focused on revenge against Genzo, his motivations evolved into the broader ambition of seizing control of Chronos's global power structure. After Chronos's worldwide takeover ("X-Day"), he formed and led the resistance group "Zeus' Thunderbolts" (Zeus No Ikazuchi), explicitly modeling his plan after the Greek myth where Zeus overthrows his father, Cronus. His actions are consistently calculated manipulations aimed squarely at usurping Chronos. His Guyver III armor possesses standard Guyver capabilities: enhanced strength, speed, and durability; regeneration; environmental protection; a head laser; sensor orbs; vibrational blades (High-Frequency Swords); a Gravity Control Orb for flight and gravity attacks; and the Mega-Smasher chest beam. Visually, Guyver III is distinct, often depicted with darker, more menacing coloring (black chitinous plates), additional spikes, and double-bladed forearm vibrational swords compared to Guyver I. Functionally, these are cosmetic differences reflecting the host, though his aggressive tactics make him a more dangerous combatant. The armor's core weakness remains the Control Medal on its forehead; its destruction is fatal. Key events define his arc. He covertly aided Sho against Chronos while manipulating him, sometimes allowing Sho to face extreme danger to further his own observations or plans. He allowed Sho to die against the Zoanoid Enzyme (his transformed uncle Genzo) to test the Guyver's regeneration via the Control Medal, later helping destroy the Chronos Japan branch. His identity was exposed to Chronos when he rescued Mizuki and Tetsuro Segawa, battling Hyper-Zoanoid Team 5. He infiltrated the buried Creator ship at Relic's Point with Sho, surviving its destruction by Chronos leader Archanfel. Awakening in Canada, he discovered Sho encased in a chrysalis. Leaving it behind, he built the Zeus' Thunderbolts resistance during Chronos's global rule. He returned to Japan after the chrysalis (containing the evolved Guyver Gigantic armor) vanished from Chronos custody. He successfully wrested control of the Gigantic armor from Sho using sheer willpower during a battle, dubbing it Gigantic Dark. However, Sho later reclaimed control permanently during Agito's battle against the Zoalords Li Yentsui and Waferdanos. This loss prompted Agito to seek a means of creating his own Gigantic armor, requiring access to a Creator ship's control mechanisms, believed located under Chronos Headquarters in Arizona. He maintains few genuine connections. His only confidants are family retainer Yohei Onuma and Yohei's granddaughter, Shizu Onuma. Shizu's devotion is absolute; she willingly underwent transformation into a proto-zoalord (Griselda) to serve Agito's cause, despite the severe cost to her lifespan. His relationship with Sho remains purely strategic, marked by manipulation and a fundamental clash of ideologies regarding power and its use.