Daisaku Kusama, a child burdened with sudden responsibility, inherits Giant Robo—a towering atomic-powered machine built by his coerced father for the terrorist group Big Fire. After his father’s death, he commands Robo through a wristwatch-like controller, forging a familial bond with the machine as his last link to his family. Orphaned young, he is raised by the International Police Organization’s Experts of Justice, who battle Big Fire’s worldwide schemes.

Depicted as 11 in early stories, he ages to 12 in the OVA timeline, tracing his evolution from a trauma-shadowed boy to a resolute agent. Without superhuman gifts, he depends on Robo’s unmatched combat strength, viewing it as a loyal ally rather than a tool. His idealism and loathing for Big Fire fuel his resolve, though simmering anger and rigid morals reveal the psychological weight of his duties.

The 2007 series *GR: Giant Robo* introduces an 18-year-old Daisaku discovering Robo in submerged ruins. Their DNA-linked bond unlocks his control over the machine, thrusting him into clashes with ancient robotic beings and covert factions. This iteration shifts focus from childhood scars to struggles with legacy and self-definition amid expanding conflicts.

Critical bonds shape his journey: Ginrei, a fellow Expert serving as a protective sibling figure, and Tetsugyu, a rival-turned-ally whose friction with Daisaku softens through shared trials. Robo’s autonomous acts to shield him blur boundaries between machine and guardian, anchoring themes of surrogate kinship.

His arc consistently grapples with balancing paternal legacy and personal choice. Early narratives fixate on trauma-fueled dependence on Robo, while later tales highlight decisive autonomy, contrasting adversaries like Genya, who spiral into inherited hatreds. This trajectory charts his path from a grieving youth to an emblem of tenacity, underscoring heroism’s sacrifices and the tangled weight of inherited purpose.