Being a gentleman is the foremost rule of Blanc College High School, to the degree that all students of the celebrated all-boys boarding school must recite the mantra on his first day of classes. However, when rumors of a vampire attack on a student threaten its pristine reputation, cold and unsociable Yuki Hasegawa starts to investigate the mystery.

Meanwhile, student council president and infamous playboy Jean Michel has taken a liking to Yuki and coerces him into performing various favors for the student government. As Yuki learns more about the blood drinkers hidden in the shadows, he discovers more secrets about Blanc College and finds his school life intertwined with Jean.