Killy Gagley is a former gangster from the Bronx who became one of the three primary pilots of the giant robot GoShogun, operating the jet known as Jack Knight that docks into the machine's right leg. He serves as a member of the team aboard the teleporting fortress Good Thunder, which travels the world to combat the malicious organization Docooga.

In the sequel film *GoShogun: The Time Étranger*, set forty years after the original series, Killy is among the former comrades who gather at the bedside of Remy Shimada as she lies in a coma following a car accident. Within the narrative of her subconscious, he participates in a shared dream where the group is trapped in a mysterious town facing a predetermined fate. In this surreal landscape, he demonstrates his continued skill as a fighter, engaging in a bar brawl and employing knives as his weapons of choice. He is also seen fighting back-to-back with his longtime teammate Shingo Hojo during these events.

His background as a gangster from the Bronx remains a consistent trait across all depictions.