Daisaku Kusama, sole heir to Dr. Kusama’s legacy, wields the wristwatch controlling Giant Robo—Earth’s mightiest automaton, forged under duress by his father for the shadowy syndicate Big Fire. Orphaned early—his mother perishing postpartum, his father killed at age six—he inherited both the device and the scientist’s crusade. By twelve, he joined the International Police Organisation’s Experts of Justice, channeling grief into a vow to dismantle Big Fire and honor his father’s final ambition.

Bound to Giant Robo by voice command and a watch forged from shared strife, Daisaku summons the machine instinctively in peril, their symbiosis a lifeline honed through years of mutual dependence. Bereft of combat prowess, he leans wholly on the robot’s might, confronting battles with raw determination and gnawing inadequacy when separated from his metallic guardian or confronting its flaws. Youthful idealism occasionally clouds his judgment, as seen in his early reverence for the Shizuma Drive’s promise—a hope later fractured by revelations of its tainted origins.

Shaped by loss and premature adulthood, Daisaku oscillates between boyish optimism and the solemnity expected of his role, adopting the Experts as surrogate kin. Ginrei, a steadfast mentor, anchors him with sisterly counsel as he navigates the labyrinth of legacy and morality. His resolve, tempered by loyalty to his father’s dream, fuels an unyielding spirit despite the toll of wielding catastrophic power and facing ethical quandaries.

His arc traces the struggle to reconcile duty with self-worth, grappling with fears of being reduced to Robo’s operator while chasing his father’s vision. Each challenge strips layers of innocence, exposing the cost of sacrifice and the weight of justice—a journey marked by the clash between the fervor of youth and the gravitas of a world’s fate resting on slender shoulders.