Zero Kiryuu (錐生 零, Kiryūu Zero)

• who is a year older than Yuki Cross, comes from a vampire hunting lineage. His family was killed by the pureblood vampire Shizuka Hio because of one of the assignments his parents carried out. Zero was taken in by the headmaster of Cross Academy and became a Prefect (Guardian), alongside Yuki Cross. He has a great hatred for vampires because of what happened to his parents, but it is later revealed that he himself is a vampire as a result of Shizuka's attack. It is also later revealed that his twin brother, Ichiru, also survived the attack and lived at Shizuka's side. After he consumes Shizuka, Kaname lets Zero drink some of his blood to keep Zero from losing control of himself in order to protect Yuki.

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Yuki Cross's earliest memory is of a snowy night in winter, when she was attacked by one vampire and was saved by another, Kaname Kuran.Yuki is the adopted daughter of the Headmaster of Cross Academy, Kaien Cross, and has grown up and become a prefect for the school with one main purpose: for vampires to coexist peacefully with humans . Her fellow guardian, Zero Kiryu, a childhood companion whose parents were killed by a pure-blood vampire, is now determined to kill them all and refuses to trust them. Through a cruel twist of fate, Zero becomes a vampire himself, having been bitten by pure-blood vampire, Shizuka Hio, four years before. Now Yuki must help him fight his curse, as well as recover the lost memories of her past. She must also discover why Kaname, who leads the group of Night class (all of which are also vampires) at Cross Academy as their President, saved her that night and what deep dark secret he is keeping from her.