Sasame Yui, a descendant of vampires, feels out of place in her high school class. Unable to fit in with her human classmates, she's often late to school — something that the class representative, Sekiya, relentlessly criticizes her for. One day, angered by Sekiya's nagging, a dark impulse flickers through Yui's mind— *\Maybe I should just… suck him dry.\* But that thought marks the beginning of something far more dangerous—an ecstasy said to surpass sexual pleasure a hundredfold. Thus begins the tragic tale of those consumed and undone by their own desires.