Yuki Cross is a first-year general education student at Cross Academy. As a member of the Disciplinary Committee, along with her childhood friend Zero Kiryu, her duty is to keep the infatuated Day Class students from chasing the beautiful Night Class students, all while performing the important task of protecting the secret of the Night Class. The secret…that all members of the Night Class are vampires!! The creation of the Night Class was an effort formed to end the long history of conflict by promoting a peaceful coexistence between human beings and vampires. As Guardians, Yuki and Zero are given the vital role of protecting the coexistence of the Day Class and the Night Class. Unlike Zero, who sees the vampires as enemies, Yuki believes vampires and humans can coexist.