The prestigious private school, Cross Academy, consists of two sessions, the Day Class and Night Class. Although the Night Class consists of students that are all beautiful, intelligent elites, they are in fact vampires!

Yuki is busy patrolling the school grounds for Day Class girls who are trying to sneak chocolates to the Night Class boys for St. Xocolatl's Day.

As a duty of the Disciplinary Committee, Yuki and Zero must conduct a surprise inspection of the students' belongings at both the Sun and the Moon Dormitories. Just as they are about to enter the Moon Dormitory, Zero suddenly leaves the school grounds. Yuki goes after him in a panic but can't find him. As she roams the streets by herself, Yuki is haunted by her memories from ten years ago, when suddenly a mysterious mother and child appear before her.