Lanterns, Lamps

In a parallel world where humans and demons coexist, a dead cat was found in a lotus pond at school.

To prevent the existence of demons from being discovered by humans, the demon world has ruled that members are not allowed to use magic on earth. This strange dead cat has aroused the suspicion of the human world. You have been sent to this school by the underworld as a detective to discover the truth.

Who is it? Who would elaborately murder a cat?