At first glance, Suitaimon is an ordinary Japanese language teacher. It seems that he lives a non-violent, non-resistive, and timid life even for bad students. However, he has a secret that must be kept secret. It is his own misfortune that he changes his hairstyle, wanders around the entertainment district night after night, and searches for young women at clubs. Yes, he is a vampire of darkness who cannot live without drinking her virgin blood. His current target is his fellow English teacher, Rumi Nitta. Imon wants to get close to him somehow, but he never gets a chance. That's no wonder, he's a vampire at night, but he's extremely weak during the day when the sun shines. Even after becoming an adviser to the volleyball club due to the principal's consideration, every day is nothing but an abomination. At that time, it is discovered that Hiroshi Saegusa, a hero of the volleyball club of another school, was toying with Imon's student. Rumi becomes enraged and presses Imon to question this outrage, but...