Recently, Berlin, where you live, has had many strange murders. The victims are female and there are always deep tooth marks on their necks. As an elite police officer, you must quickly catch the murderer who is spreading terror to Germany.

After being chased home by the police chief with the excuse that "You will die from hard work", you had to bring the case documents home to study.

Suddenly, there is a knock on the door, you open the door and saw Nagi Seishiro, your lazy roommate.