Rabi stands as one of three primary Madou Warrior protagonists, wielding water-elemental power. His magic top summons the Madou King robot Aquabeat.

Physically tall and light-skinned, Rabi possesses long, messy blonde hair and dark green eyes, marked by an X-shaped scar on his cheek. He typically wears a white headband that often conceals his rabbit-like ears. His attire consists of a light blue T-shirt with darker blue trim, matching pants, dark blue thigh-high boots, a white sash draped over one shoulder, and white fingerless gloves.

Initially, Rabi maintains a rude, self-centered, and distrustful attitude, preferring solitude after years without known family or friends. This isolation fuels his reluctance to accept comrades Daichi and Gus, leading to frequent attempts to one-up Daichi. His integration into the group is gradual and marked by conflict, including a temporary departure following a mission setback.

His background is later revealed as Marius von Ramas, grandson of the Long-Eared Tribe grandmage V-Ramas, connecting him directly to the tribe endangered by the Jadou Clan. Later lore identifies him as a half-breed, born to a Long-Eared father and an Earthling mother, cited as the source of his exceptional magical potential.

A pivotal turning point occurs when Jadou Clan leader Lord Agramant is unveiled as Rabi's corrupted grandfather, V-Ramas. Rabi is captured, brainwashed by the Jadou forces, and compelled to aid in awakening the Great Lord of Darkness while turning against Daichi and Gus. He is liberated only by the intervention of the Black Warrior – later revealed as his mother, Sayuri – who attacks Lord Agramant from within the enemy structure.

Following these events and the primary conflict's resolution, Rabi reconciles with his heritage and familial connections, shifting from his isolated existence toward acceptance within a restored community.