OVA
Description
Daisaku Kusama, the only son of the coerced creator of Giant Robo, Dr. Kusama, lost his mother early and then his father when Big Fire executed him for secretly coding the robot to obey only Daisaku. At six, he inherited the special wristwatch control device and became Giant Robo's sole master.

By twelve, Daisaku was a full member of the International Police Organisation's Experts of Justice, opposing Big Fire. Though he possesses no superhuman abilities or advanced combat training, he commands the 30-meter-tall, nuclear-powered Giant Robo, Earth's most powerful robot. The wristwatch, a radio transmitter, responds exclusively to his voice, and the robot features an auto-guard circuit that activates if Daisaku is endangered.

His character is forged by traumatic parental loss and the weight of commanding Giant Robo. He retains a measure of childish optimism yet was forced into premature maturity. He develops a strong bond with the robot, treating it as a friend and, for a time, his only family. This idealism is often tempered by frustration and helplessness when unable to operate the robot or when facing its limitations.

Within the Experts of Justice, Daisaku forges significant bonds: Ginrei becomes a protective older sister figure, Taisou a wise mentor and father figure, and Tetsugyu, after initial resentment, develops a fondness for him, providing crucial human connection and guidance.

Daisaku is a fervent supporter of the world-changing clean energy Shizuma Drive until he uncovers its dark past and connection to the Tragedy of Bashtarle, a global energy failure that caused massive loss of life, a revelation that deeply challenges his idealism.

In the GR: Giant Robo anime series, a reimagining set in a different continuity, Daisaku is an 18-year-old scuba diving guide in Okinawa. He discovers Giant Robo, designated GR-1, in underwater ruins, and his DNA is rewritten, bonding him body and spirit with the ancient machine. This version battles the terrorist organization Gigantic Rebellion Operators (GRO) and uncovers the true nature of the GR units as ancient weapons built to combat eldritch beings known as The Old Ones.