Akutabe is a central figure in the Yondemasu yo, Azazel-san franchise, operating as a private investigator who runs his own detective agency. His background is shrouded in mystery; his first name is unknown, and it is even unclear if he is entirely human. He was born on August 6th, though his age is never specified, and he has a deep, obsessive interest in the occult, spending an unhealthy amount of time reading and collecting grimoires from around the world, sometimes resorting to theft to acquire them. He claims to collect these dangerous books to prevent them from falling into evil hands, but his true motives remain ambiguous. He took in a rowdy teenage boy named Kotaro Dochin after the boy's grandfather, an old friend of Akutabe, passed away.

In terms of personality, Akutabe presents a calm, polite, and professional demeanor when dealing with human clients. However, this facade hides a callous, strict, and profoundly sadistic nature that is primarily directed at the demons he summons. He is short-tempered and vicious towards supernatural beings, who are all terrified of him, often referring to him as "The Devil". He seems to enjoy witnessing the ugly side of human nature and expects the worst from people, yet he operates with a personal moral code that forbids resorting to murder. Despite his cruelty, he has a notable soft spot for his part-time assistant, Rinko Sakuma, treating her with more patience and respect than anyone else, for reasons that are not fully explained. He is also kinder to most humans and acts as a reluctant guardian to Kotaro, showing hints of a softer side as the series progresses.

Akutabe's primary role in the story is as the head of the Akutabe Detective Agency and a demon contractor. He uses his vast knowledge of the occult to summon demons and force them into contracts, employing their abilities to solve his clients' cases. He serves as a mentor and employer to Sakuma, introducing her to the world of demon summoning. His power is so overwhelming that the series frequently creates excuses for his absence to allow for conflict to develop among the other characters. His main motivation for his work remains enigmatic, but he is dedicated to using demons to solve cases efficiently and is obsessed with acquiring grimoires, which he keeps locked away.

Akutabe's key relationships are defined by dominance and utility. He employs Sakuma and seems intent on keeping her at the agency, viewing her as a mentee and holding himself responsible for her safety, even breaking through an interdimensional barrier to rescue her. With the demons under his employ, such as Azazel and Beelzebub, he is a terrifying and unforgiving bad boss who regularly subjects them to brutal physical punishments for disobedience or failure. He has a contract with the demon Undine, whom he is not above emotionally manipulating by feigning affection to make use of her powers. He shows a begrudging tolerance for Beelzebub, finding him more responsible than Azazel. In contrast, he is civil and polite to his human clients and acts as a provider and guardian to Kotaro.

Akutabe's character development is subtle and largely tied to the slow revelation of his mysterious nature rather than a change in his personality. He remains a stoic, powerful, and enigmatic force throughout the series. The most significant developments involve hints at his true identity. It is implied that he possesses a monstrous "true form," and witnessing this form caused the powerful demon Moloch II to become deathly pale and his hair to turn white from shock. Later in the manga, he reveals a special third eye on his forehead, which is associated with godhood in the series' universe, further suggesting he is not an ordinary human. He also demonstrates a possessive obsession with collecting grimoires and keeping them from being misused, which provides some insight into his motivations.

Akutabe possesses a formidable array of notable abilities. He is an expert demon summoner who can summon and bind a wide variety of demons to his will. His most iconic tool is the Solomon Ring, a restricting force that significantly reduces the power and size of the demons he summons, making them appear in chibi-like forms. He is uniquely immune to most demonic abilities, able to casually swat away or nullify powerful attacks such as Beelzebub's forced defecation ability. He possesses immense, seemingly supernatural physical strength, capable of killing and torturing demons without touching them, breaking through dimensional barriers with his punches and kicks, and fighting hand-to-hand with giant mechanized demons. He is also an intuitive detective with a high level of intelligence, strategic thinking, and vast knowledge of history and the occult, allowing him to solve any case he is given.