TV-Series
Description
Kōtarō Dōchin is a 13-year-old middle school student affiliated with the Akutabe Detective Agency after being taken in by Akutabe. This arrangement follows his grandfather's death, as the grandfather was an old acquaintance of Akutabe and Kōtarō has no other surviving relatives, placing him under Akutabe's guardianship.

He possesses a mischievous and verbally abusive personality, frequently plotting against Akutabe or attempting to manipulate situations for personal gain. These schemes often backfire due to his lack of foresight and intelligence, resulting in unintended consequences. Kōtarō harbors a fascination with voyeurism, particularly involving naked women, serving as a recurring character trait and source of comedic distraction. He frequently attempts to present himself as an innocent child to manipulate others, though this facade is easily seen through by those around him.

As a demon contractor, Kōtarō formed a pact with Gusion, one of Solomon's 72 demons, using a high-ranked grimoire inherited from his grandfather. To secure this contract, he sacrificed the memories of his grandfather. Gusion's ability, "Forgetfulness," consumes the memories of others, especially cherished ones, which Kōtarō exploits to evade responsibility or cover up his mistakes.

Tasked with attending Golgotha Middle School under Akutabe's supervision, Kōtarō accidentally breaks a vase in the principal's office. He summons Gusion to erase the memories of his homeroom teacher, Himoi, and the principal to avoid repercussions. This action inadvertently triggers a chain of events: the demon Undine, obsessed with Himoi, transforms the school into a dystopian environment after feeling rejected. Kōtarō eventually resolves the chaos by manipulating Undine's emotional state to reverse her transformations and again uses Gusion's memory-erasure ability to make everyone forget the incident.

Kōtarō frequently expresses frustration that the adults in his life, particularly Akutabe and Sakuma, refuse to assist him with problems he created himself. Despite his antagonistic behavior, he demonstrates occasional resourcefulness in rectifying self-inflicted situations, such as leveraging demonic abilities to reset collateral damage.

His appearance consistently features black, spiky hair and a school uniform, aligning with his student status. The manga implies he resides at the detective agency, while the anime adaptation does not explicitly confirm his living arrangements.