Belzebuth acts as Claude Jeanne Ellmeyer's close aide and fiercely loyal bodyguard, reacting with zero tolerance to any disrespect toward the Demon Lord. He presents a rough, easily provoked exterior, often using anger to conceal underlying softer emotions—a defensive trait stemming from his lack of exposure to noble court etiquette within Claude's small demon court. His distinctive horns enhance an intimidating presence that contrasts his complex nature.

His interactions with Aileen Lauren d'Autriche significantly shape his development. She instructs him in proper manners and social etiquette, lessons he genuinely appreciates, fostering deep loyalty and respect toward her. This guidance strengthens his commitment to supporting both Aileen and Claude. Belzebuth's personality blends a protective, people-pleasing instinct with occasional lapses in common sense. These lapses lead to unintentionally humorous incidents, such as mishandling poison or accidentally starting fires, making him a relatable, unconventional figure in Claude's inner circle.

Throughout the narrative, Belzebuth actively works to maintain the stability of Claude and Aileen's relationship. After Claude suffers memory loss from an injury, Belzebuth collaborates with allies like Keith Eigrid on plans to restore Claude and Aileen's engagement. His dedication to Claude's well-being remains steadfast amidst complex political and personal challenges. While his background origins remain unspecified, his role consistently emphasizes unwavering service and gradual personal growth in navigating human nobility and emotional dynamics.