Yuki Cross is a first-year student at Cross Academy. As a member of the Disciplinary Committee, 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, that all members of the Night Class are, in fact, vampires! The Night Class was intended to end a long history of conflict by promoting a peaceful coexistence between human beings and vampires. As Guardians, Yuki and her childhood friend Zero are tasked with 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.