Sakuma is a college student who works part time at the Akutabe detective agency. There she does regular office work for private investigator Akutabe. However, Sakuma soon learns that Akutabe is no ordinary detective, but in fact a demon detective. He is able to summon demons through the use of a grimoire and use each of their special abilities by providing an offering. He uses their magical powers to solve the case he is working on and he wants Sakuma to start learning demon summoning. As Sakuma begins her journey to be a demon detective, little does she know the repercussions of using demons.

It is the 23rd century, an age of science and technology, where sex is no longer required to reproduce. However, humanity has not forgotten sex! Sex has evolved to become a form of martial arts, and those who practice it are known throughout the world as BattleSexers!