Sakyo Asahina is a university lecturer who happily talks about bizarre murders under the nickname of "Psycho-sensei." The person who came to see him was the chief of the detective department of the Metropolitan Police Department, who is now talking about the serial killer who is making headlines in the media. However, the two are already acquainted. 15 years ago, at the scene of a murder. The culprit who survived at that time is now released from prison and is making a new case. And Sakyo starts to move!