Kojo Akatsuki is suspected of being the Fourth Progenitor, a strong vampire who might potentially disturb the balance of power among the world's three governing progenitors, on Itogami Island, a man-made island south of Japan that has turned into a monster and demon refuge Before becoming a vampire, Kojo was a regular high school student who is hesitant to utilize his talents, which he barely manages. Yukina Himeragi is a new Sword Shaman, and his first duty is to 'observe' him. Kojo soon becomes the focus of many who are concerned about the dangers he symbolizes. Kojo and Yukina make friends with a variety of students and others, some of whom are drawn to Kojo and their circumstances fuel his libido, which is the cause of much of his lust.