Ganrikiman is an assassin robot deployed by the criminal organization BAD, appearing as the primary antagonist of the fourteenth episode of Robot Keiji. His physical design is distinctive, featuring an inverted triangular face reminiscent of an ant or a bee, dominated by large, oversized eyes. These eyes are his most formidable weapon, capable of emitting a powerful death ray that can kill a human being instantly upon direct contact and is strong enough to shatter concrete and other non-living materials. In addition to this optical weapon, his right arm can be reconfigured into a Gatling gun for sustained projectile attacks, and he also possesses a blade-like extension for close-quarters combat. Another notable physical trait is his ability to extend his neck to a considerable length, allowing him to peer into windows or attack from unexpected angles.

Ganrikiman operates as a transactional agent for BAD, embodying the organization's businesslike approach to crime. He is loaned to human criminals who require his specific abilities to carry out their plans, with the understanding that half of the proceeds from the crime will be returned to BAD. In his sole appearance, he is contracted by Kouzo Tanimura and Tahei Ikejima, a pair of thieves plotting a jewel heist. His motivation is purely professional and mercenary; he shows no personal malice but carries out his assignments with ruthless efficiency, demonstrating a cold and businesslike demeanor. He refers to the human detective robot K with contempt, calling him a robot who has stooped to becoming a slave to humans.

In the story, Ganrikiman serves as a specialized obstacle that directly challenges K's capabilities. His death ray proves particularly dangerous, as it disrupts K's directional radar and blinds him temporarily during their first encounter, forcing K to retreat. This defeat prompts K to seek help from Mother, his creator, who provides him with a special optical lens that deflects Ganrikiman's death ray, making it harmless. This development is key to K's eventual victory. After K is upgraded with the lens, he confronts Ganrikiman again and, after a prolonged battle, destroys him with a flame attack that causes the assassin robot to overheat and explode. Ganrikiman has no significant relationships beyond his transactional connection to BAD and his human clients; his role is that of a deadly, single-purpose tool sent to eliminate obstacles and complete a specific criminal objective. He does not undergo any character development, remaining a static and entirely antagonistic force throughout the episode.