Yuki's childhood best friend. Zero is also a Cross Academy Guardian and likewise on the disciplinary committee. Yuki has cared about him as a close friend ever since he was brought into their home (the Headmaster's). His family, one of vampire hunters, was murdered by the pureblood vampire Shizuka Hiou when he was young. He harbors a deep hatred for vampires and claims to have taken on the role of Guardian to learn how to hunt them better. In truth, Zero was bitten during the attack on his family and therefore was turned into a vampire, something that has been kept secret even from Yuki until his vampiric urges began to surface and became uncontrollable. As Zero's body rejects the blood tablets that most vampires take to control their hunger, Yuki began letting him drink her own blood, which helps his thirst for blood, but he is ultimately to become a Level E vampire. The story implies that Zero harbors romantic feelings for Yuki. In chapter 35, he discovers Yuki is a vampire, and in chapter 37 he aims his gun at her which could have been because he is angry with himself for not keeping his promise to her not to become a vampire, which leads to Yuki telling him her vampire side "ate" her other side. He "almost" kissed Yuki twice showing that he has feelings for her. He has also stated to Yuki that he would not have been able to live or cope with this if it wasn't for her.