Requested by Mangakid
Zero Kiryu is unique being both a Vampire Hunter and a vampire. Yuki's close friend and a Cross Academy Guardian, he was trained to be a Vampire Hunter by Toga Yagari. Zero carries the anti-vampire gun called "Bloody Rose”. Zero lives with Kaien Cross and Yuki, after being bitten by a pureblood vampire who also murdered his family. Due to the attack, Zero developed a deep hatred and distrust of vampires, despite originally being a gentle character by nature. Matsuri Hino described Zero as exemplifying her hesitant nature. The first arc of the story is spent dealing with Zero trying to overcome his fall into the madness, helped by Yuki when she pledges to feed him her blood. Yuki continually oversteps boundaries in helping Zero and he ends up preventing her from trading her humanity to Shizuka Hio in exchange for preventing his fall to a Level E vampire. Zero swears never to allow Yuki to become a vampire and attempts to help her with her own issues. Zero clashes with Kaname Kuran, who only allows Zero to live to protect Yuki and Zero is eventually forced to drink the blood of Kaname to delay becoming a level E vampire. Following the discovery of Yuki's true nature as a pureblood vampire, Zero and Yuki's friendship is broken. (Information used from wikipedia).