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!

It's been one year since Yuki left Cross Academy with Kaname, and tonight is her first vampire soirée as a pureblood. Her best friend Sayori has snuck into the party to see her, but will Yuki and Zero be able to protect a human girl amid a bevy of vampires?