Zero Kiryu

Zero Kiryu (錐生 零, Kiryū Zero?) is one of the main characters of Vampire Knight. Zero is Yuki's close friend and the only other Cross Academy Guardian. Zero carries an anti-vampire gun named "Bloody Rose," given to him by Kaien Cross.

Personality
As a child, Zero was a quiet and gentle boy, his twin, Ichiru questioned whether he was even capable of being a hunter. However after Shizuka's attack, Zero developed a deep hatred and distrust of vampires, he became withdrawn and sullen. He sports a scary aura that makes most of the day class students wary of him.

Zero can also be very cruel and ungrateful, especially to Yuuki. Immediately after Yuuki is changed into a Pureblood vampire, and she tries to see him, Zero refers to her as an arrogant pureblood who trifles around with other people's lives, despite her kindness and altruism. Although Yuuki does not harm or threaten anyone, Zero automatically classifies her as an enemy just for being a pureblood, showing no appreciation of the kindness she has shown to him in the past.

Appearance
Zero has short silver hair with long bangs and grayish purple eyes that seem emotionless most of the time, they glow blood red when he loses to the blood lust. He has very pale skin, even paler than the Night Class students. He is 181 cm tall .He bears a tattoo on the left side of his neck that seems to look like a cross between a star and a flower. It was supposed to keep him from turning into a vampire. He is usually shown in his black 'day' class uniform which he wears incorrectly with the vest and red tie exposed from under his black jacket.

Background
Zero is descended from Vampire Hunters and was trained as a Vampire Hunter by Toga Yagari. Four years ago, Zero was taken in by Kaien Cross as the sole survivor of a murderous attack on his family by Shizuka Hiou. Zero was bitten during the attack and has spent the last four years resisting turning into a vampire. Zero was tattooed with a symbol on his neck that helped suppress the vampire awakening.

Plot Summary
Zero kept his vampire secret from Yuuki until bloodlust overwhelmed him and he bit Yuuki. Zero attempted to run away, stopped by Yuuki, who pledged to kill Zero should he fall to level E. Following Zero's awakening as a vampire, his tattoo was used by Kaien Cross to allow Yuuki to tame Zero. Zero's body rejected the blood tablets used to sate a vampire's thirst, thus Yuuki convinced Zero to continue drinking her blood.

Zero harbored romantic feelings for Yuuki, however he supported Yuuki's feelings for Kaname Kuran. Zero prevented Yuuki from becoming a vampire when attempting to trade for Shizuka's blood that would have saved Zero. He fought his master's compulsion and shot Shizuka to stop her biting Yuuki. Zero swears he will never let Yuuki become a vampire. Zero is prevented from drinking Shizuka's blood finding her already dead. In order to gain control and delay the fall into madness becoming a level E vampire, Zero was convinced to drink the blood of the pureblood, Kaname Kuran. Following Zero's discovery that Yuuki is actually a pureblood vampire, Zero severed his friendship with her and likewise Yuuki told him her vampire side "ate" her other side.

Though Zero regained his sanity, the Hunters Association have him locked up, arrested by Yagari. Kaname revealed that his purpose in strengthening Zero was in order for him to protect Yuuki and defeat Rido Kuran. Zero is shot by his twin brother and finally completed the Twin Hunter fragment after he is convinced to "eat" the dying Ichiru. With this act, along with being a twin vampire hunter of excellent lineage who has become a vampire, within Zero is the blood of three purebloods, Yuuki, Kaname and by proxy Shizuka, making Zero one of the most powerful characters in the series and saving him from becoming a Level E.

Zero's new powers are shown to be manipulation of vines within his body that are an extension of the Bloody Rose, which is capable of stopping Yuuki's evolved Artemis Rod. Zero declared Yuuki his enemy and attempted to keep her out of his fight with Rido. When Yuuki struck the deadly blow to Rido's heart, Zero completed the destruction. Zero then turns the Bloody rose on Yuuki and reveals his intention to kill all pureblood vampires including her. Zero hugs Yuuki and kisses her, finally telling her that he loves her.As the two pull away from their embrace, Zero tells Yuuki that the next time they meet, he'll kill her. As Yuuki leaves the Academy, they see each other as Zero carries Ichiru's dead body. Yuuki looks at him with sad eyes and Zero appears to be glaring.

It is later revealed that since the say Yuuki left the academy he has been able to take the blood tablets. He is to be made President of the Vampire Association in the future due to his strength and ability to intimidate others. He is opposed to make peace with the vampires again and feels he was tamed by Yuuki (or as stated by another hunter "little Kuran missie").