Kerubero-kun is a demon distinguished by his unconventional physical design: grey hair, golden eyes, and a primary head complemented by two additional heads attached to his hands, functioning as glove-like appendages. This contrasts with traditional three-headed hellhound depictions. His attire includes a Japanese-style kindergarten uniform, a protective helmet, and a dog collar.

Typically well-mannered, he exhibits extreme emotional volatility concerning Sakyuba-chan, fueled by intense romantic feelings. This infatuation triggers fierce jealousy during interactions between Sakyuba-chan and Kiichi. In such instances, Kerubero-kun projects fire from his hand-based heads, consistently resulting in Kiichi being set ablaze. His fire manifestation and reactive jealousy remain defining traits.