Cross Academy is attended by two groups of students: the Day Class and the Night Class. At twilight, when the students of the Day Class return to their dorm, they cross paths with the Night Class on their way to school. Yuki Cross and Zero Kiryu are the Guardians of the school, protecting the Day Class from the Academy's dark secret: the Night Class is full of vampires!

The Night Class is back in session, but Yuki finds herself quickly becoming second fiddle to Sara Shirabuki. With Kaname gone, Yuki is now desperate for blood, so Zero offers her his own. Will she break her promise to Kaname and drink from Zero?