Killy Gagler is a tough, street-smart pilot from the Bronx with a gangster background. He operates the Jack Knight jet, which docks inside the right leg of the giant robot GoShogun. As a member of the crew aboard the teleporting fortress Good Thunder, he fights the evil organization Dokuga alongside his close-knit teammates Remy Shimada and Shingo Hojo.

During missions, Killy engages in lighthearted flirtatious banter with Remy, a dynamic that serves as a coping mechanism for the stress of combat and confinement. A reliable and skilled combatant, he participates in operating both the weaker Tri-3 formation and the powerful GoShogun robot.

Four decades after their initial conflicts, Killy reunites with his former teammates at the hospital bedside of a critically injured Remy Shimada. In the dream world of her comatose mind, the team wears military fatigues and works together to aid her, reflecting their enduring bond. Within these surreal dream sequences, Killy is shown attempting to write a novel, suggesting personal aspirations beyond his life as a soldier.