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!

Zero warns Yuki to stay away from Maria Kurenai, the new Night Class transfer student, although he won't tell Yuki why. Kaname is also wary, and he sends Ichijo to watch Maria so she doesn't start trouble. Who is this girl, and why does she have the entire Night Class on edge?