Judgment Nezuya, legally named Seigi Nezuya, serves as a Grand Paladin operative protecting Earth from extraterrestrial dangers. His given name "Seigi," translating to "justice," clashes ironically with his lineage of sake brewing—contradicting his assertion that his father destined him for law. This duality underscores a performative layer to his identity.

He displays a flamboyant, theatrical demeanor, infusing dramatic flair into his actions and speech. Despite his mature exterior, his deep engagement with geek culture creates an eccentric persona, widening the gap between his appearance and interests. He occasionally revisits his old high school's Occult Research Club, preserving academic ties.

Within Grand Paladin, he pilots a mouse-themed mecha, consistent with the team's animal motifs. His duties involve battling Nebula Weapons—alien entities embodying human psychological insecurities. During one skirmish, a Nebula beast traps him in a hallucination exploiting his vulnerabilities, triggering a comatose state. This incapacitation spans multiple episodes, diminishing Grand Paladin's effectiveness.

His prolonged unconsciousness persists through critical events, including Harumi Kumashiro's draconic transformation and Grand Paladin's internal fracturing. As core members defect or lose powers, he remains inactive and sidelined. The documented media offers no details on his awakening, ultimate fate, or activities beyond these events.

Background specifics—such as family dynamics or pre-Grand Paladin history—receive no elaboration in available sources. Similarly, his development in supplementary media like manga, films, or spin-offs lacks documentation.