Akutabe operates a detective agency specializing in occult investigations, uniquely staffed by demons he summons and controls to solve cases. His origins are mysterious, with no confirmed age or full name, and some suspect he may not be human after a demon uncovered a hidden truth about his identity and fled in terror. He amasses dangerous grimoires from around the world, ostensibly to prevent their misuse, though his deeper intentions remain unclear. Akutabe is known for extreme strictness, cruelty, and sadism toward demons, who universally dread him as "The Devil." With human clients, he maintains a calm, polite facade while privately savoring glimpses of human depravity. Despite this harshness, he shows unexpected patience and respect for his assistant, Rinko Sakuma, mentoring her in occult arts, warning her of summoning dangers, and protecting her from interdimensional threats. He also acts as a guardian to Kotaro Dōchin, the grandson of an old associate, gradually revealing warmth toward the boy. Visually, Akutabe has sharp, spiky black hair and favors a black business suit with a tie; his dark eyes intensify, glowing red or purple when he is enraged. He is often seen reading diverse materials, from ancient grimoires to children's books. His formidable abilities include contracting and summoning demons, greatly enhanced by the Solomon Ring that restricts their power. He wields supernatural strength, can shatter dimensional barriers, and demonstrates complete immunity to demonic powers, effortlessly nullifying attacks. His expertise spans deduction, spellcraft, and the occult, allowing him to perform complex rituals without consulting grimoires. Akutabe’s relationships starkly contrast his treatment of humans and demons: he is fiercely protective of Sakuma, manipulates the demon Undine through feigned affection, and subjects demons like Azazel and Beelzebub to relentless physical abuse while tolerating their failures for their utility. His fearsome reputation intimidates even high-ranking demons. Unresolved enigmas persist, including his true identity and monthly mood fluctuations that heighten his senses.