Zero Kiryu

Zero Kiryu (錐生 零, Kiryū Zero) is one of the main characters of Vampire Knight. Zero is Yuki's childhood friend and the only other Cross Academy Guardian. Zero carries an anti-vampire gun named "Bloody Rose" around, which he uses to attack vampires or for shooting target practices.

Character concept
Even before becoming a vampire, Zero Kiryu was noted to be a talented vampire hunter due to being the stronger of a pair of rare twin hunters, his twin is Ichiru. Zero is an honest character with an affection towards Yuki's kind heart.

Appearance
Zero is considered attractive by a few Day Class girls though intimidating by others. Zero bears a tattoo, the Hunter's Seal, on the left side of his neck originally used to suppress his vampire side, later used to tame him. Zero is a casual dresser, usually wearing school uniform incorrectly with the vest and red tie exposed from under his black jacket and wears three silver earings on his left ear (top) and 2 on his right (bottom). His hair is a pale, silvery white, he had impressively pale skin well before being transformed, and his eyes are pale purple or lavender coloured.

Personality
As a child, Zero was a quiet and gentle boy, to the limit where Ichiru questioned whether or not he was even capable of being a vampire hunter. However after Shizuka's attack, Zero developed a strong distrust of vampires. Zero is a tsundere character, he sports a scary aura that makes most of the Day Class students wary of him, he can also glare in a way that even Kaname Kuran calls it scary. However, his innate nature is to protect humans, his cold attitude towards those he loves is likely to push them away and keep everyone at a distance. He also happens to be a stickler for details, as he doesn't consider himself as an adopted son of Kaien's family with Yuki, or holds all the details about how vampires and humans can be similar in their own ways. As told by Ichiru to Kaien, Zero's favorite food is vegetable soup.

Following his full awakening into a vampire, Zero harbors a great disgust towards himself because of inability to control his hunger and reliance on Yuki. His dismal outlook on his future and fear of what he might do causes him to give up and he almost kills himself with his anti-vampire gun, The Bloody Rose. He ignores his hunger to the point of starvation rather than go to Yuki. He tries to help Yuki resolve her own problems and then impresses upon her that its alright for her to burden and use him because she owns him.

Zero is hostile to the Night Class vampires when they threaten him, however he adopts his standard tsundere attitude when engaging them one on one retaining a level of civility. Zero expresses a great deal of anger toward Purebloods because of their mechanisms in his life in particular, he extends this hostility toward Yuki as well after she turns into a Pureblood vampire. In spite of this, his sense of duty overrides his issues ensuring his reliability and trustworthiness.

Plot background
Zero was born to a prestigious vampire hunter's family. Zero, along with his identical twin brother, Ichiru, and Kaito Takamiya, were trained as vampire hunters by Toga Yagari who frequently looked after the twins when Zero's parents were out hunting. Yagari lost an eye protecting Zero, when the still naive Zero made himself vulnerable to ex-human vampire when the nurse turned wild and tried attacking Zero due to her Level E state. This was Zero's first lesson on the danger of seemingly innocent vampires, Zero promises Yagari that he will never regret losing his eye to protect Zero.

One afternoon in winter, Zero and Ichiru were walking when the came across a woman sitting in a tree. Ichiru was amazed at how beautiful she was but Zero glared at her whispering to ichiru that she was a vampire and to keep a distance. Ichiru ignored him and the following day snuck out to find the woman. Zero knew what had happened and went to find Ichiru but instead was taken himself. The woman murdered his parents and attacked Zero, biting him. That night as Zero lay struggling for life on the floor, the woman walked over to him and smiled cruely, she taunted him about the pain of being bitten and explained that this was her revenge on his parents.

After that attack Zero was taken in by Kaien Cross. Yuki approached him carefully and cared for him although he was cold and hostile at times to her. Zero kept his affection for her to himself due to her loving Kaname Kuran. Zero failed to reveal that he was going to turn into a vampire after Yuki revealed she was afraid of all other vampires, but revealed what he had become when he bit her, bringing her fears back. Yuki was a true friend to Zero and promised to always be by his side no matter what the consequences of their actions were.

Relationships
Yuki Cross

Yuki Cross and Zero Kiryu became childhood friends after he went to live with Kaien Cross after the massacre by Shizuka on he and his family. Zero harbors an unrequited love for her, except he kept it hidden for a long time because he knows she loves Kaname and only revealed it to her after he killed Rido.

Ichiru Kiryu
Ichiru's is Zero's identical twin whom he was close to as a child. For a time, they were hostile to each other because of Shizuka Hio but they became close again just before Ichiru's death.

Shizuka Hio
The pureblood Shizuka became Zero's master after she bit him the night of the attack on his family. She claims she did it because she knew that Zero would challenge her and become strong. Shizuka meets Zero again 4 years later at Cross Academy disguising in the body of Maria Kurenai, but thanks to Touga Yagari's warning, Zero recognises who she really is. She taunts him about being his master and him being under her command. He despises her for all she did; killing his parents and took his brother away as well as his own human self. When Yuki bargains her humanity for Zero's life, Zero overcomes his master's commands and manages to wound her. Zero had every intention of sacrificing his life to kill Shizuka, but is prevented by Yuki and though the final kill was not his, he was blamed for it by the council and Ichiru.

Kaname Kuran
Zero disliked Kaname on sight recognising him as a vampire and has been his rival ever since. They are only friendly to each other for the sake of Yuki Cross and Kaname can be often seen jealous of Zero when Yuki expresses care for him.

Akatsuki Kain
Akatsuki Kain and Zero Kiryu do not appear to have a close friendship (especially after Zero easily threw him.) When asked in the Offical Vampire Knight Fanbook's Vam Fan Hall (the "Zero Version") if he had to be friends with one of the night class students, Zero answered, '''No-one, of course. Wait, I have to choose someone? Well, I guess that Kain guy MIGHT be someone I could manage with.' ''

Hanabusa Aido
Zero and Hanabusa have always had a negative feeling towards each other. Hanabusa especially gets very irritated when Zero does anything to Kaname that is harmful or disrespectful e.g. when he roughly pulls Kaname's arm away from Yuki's face and when he challenges him etc. Zero does not appear to have a personal grudge to him, but maintains an adverse relationship due to his general disliking towards all vampires. Hanabusa, however does advise Zero on one occasion when he realizes Maria Kurenai could be possessed by Shizuka Hio.

Powers
Zero is a highly talented vampire hunter and possesses the standard abilities to sense vampires from a great distance, accelerated healing and in spite of being a vampire, also able to wield anti-vampire weapons. Since he became a vampire, Zero is able to distinguish purebloods from other vampires and has gained improved healing abilities. Kuran Kaname explains that after he eats Ichiru he would become the world's strongest hunter. He, then, explains that he has the blood of Kuran Yuki because Yuki was a pureblood, Kaname and Shizuka was as well. After completing the fragment Zero is able to transform the Bloody Rose into its evolved state, where it literally becomes a part of his body, however the cost is using a high amount of his blood.

Quotes

 * "Even if I loathe vampires...Even if I don't want to hurt anyone...I can't stop myself from lusting for blood." - source?

Trivia

 * Zero's first name is the kanji for rei, meaning "zero."
 * In his last name, Kiryu, the ki means "auger" or "drill," and the ryu means "life."
 * Zero is the only Vampire/Vampire Hunter to appear in the series.