After suffering a crushing defeat against a legendary detective, James Moriarty is reincarnated as a ghost in another world. He wakes up in the body of Sherry Moriarty—a severely bullied student from the elitist All Blue Academy—and manages to save the young woman, who was attempting to take her own life.

Although James has forgotten his name and past, he has retained his criminal expertise and is determined to help Sherry get revenge against Porgrette Whey Cochon and the other noblewomen who have made Sherry's existence miserable. The bullies of All Blue Academy will learn the hard way that when two Moriartys unite to commit the perfect crime, no one can stand in their way.