Ten years earlier, a Pureblood vampire, Kaname Kuran, saved Yuki Cross from another vampire's attack. Now, Yuki is a Guardian at Cross Academy, where the Night Class and Day Class students live side by side in relative harmony-despite the fact that the Night Class students are all vampires! Yuki and her partner Zero keep watch over the Day Class and protect the Night Class's secret. With Kaname's help, a peaceful coexistence has been maintained so far, but a looming shadow is about to be cast over their world...