Sakuma is a college student who holds a part-time job at the Akutabe detective agency. There, she performs routine office duties for private investigator Akutabe. However, Sakuma soon discovers that Akutabe is not an ordinary detective, but rather a demon detective. He can summon demons using a grimoire and utilize their special abilities by providing offerings. He employs their magical powers to solve the cases he is handling and wants Sakuma to begin learning demon summoning. As Sakuma starts her journey to become a demon detective, she has no idea of the repercussions of using demons...