Yuki Cross's earliest memory is of being attacked by a vampire and being saved by Kaname Kuran, also a vampire. Ten years later, Yuki and vampire hunter Zero Kiryu attend Cross Academy as school guardians protecting the "Day Class" of human students from the "Night Class" of vampires. The story follows Yuki's discovery that her childhood friend, Zero, has spent the last four years trying to fight his transformation into a vampire, and he has finally succumbed. Yuki struggles to help Zero fight his bloodlust, although it might pull her further away from Kaname. The situation intensifies when a new student, Maria Kurenai, transfers to the Night Class, and she seems to have something to do with Zero's past.