Zero Kiryu

Zero Kiryu (錐生 零, Kiryū Zero) is the main male protagonist of the series. He is both an ex-human vampire and a vampire hunter. Zero is the older twin brother of Ichiru Kiryu.

Appearance
Zero is a tall young man with silky silver hair, snowy-white skin and lavender eyes, the latter varying in shade from the manga to anime. Zero is a casual dresser and is usually wearing his school uniform incorrectly with the vest and red tie exposed from under his black jacket. He also wears five silver earrings; three on his left ear cartilage (top) and two on his right (bottom). Zero bears a tattoo, the Hunter's Seal, on the left side of his neck originally used to suppress his vampire side, and later used to tame him. He has grown taller as the series progresses.

Zero is considered to be attractive and handsome, by both Day and Night Class students

Personality
Zero is generally a composed person he is also protective of Yuki. Before the second 'part' he showed human Yuki his emotions and did not usually act hostile, and cold hearted, as he usually seemed to be towards the other Cross academy students. When Yuki was revealed to be a Pureblood vampire, he became cold and hostile, especially towards Kaname and Yuki. Though he appears otherwise, he is a gentle and kind person. Due to his childhood, he builds barriers around himself, rather than opening up to Yuki when they first got to know each other, a trait that is still evident even in the latest chapters of the manga. Yet despite this, he has a kind heart which longs to protect humans, he will never betray the ones he holds dear.

As a child, Zero was once a quiet and gentle boy, to the point that Ichiru questioned whether or not he was even capable of being a vampire hunter. However, after Shizuka's attack, Zero developed a strong hatred towards 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 scary. However, his innate nature is to protect humans, and his cold attitude towards those he loves is likely to push them away and keep everyone at a distance.

Following his full awakening as a vampire, Zero harbors a great disgust towards himself because of his inability to control his hunger and his reliance on Yuki. His dismal outlook on his future and fear of what he might do if he becomes a level E, that causes him to give up and he almost kill himself with his anti-vampire gun - the Bloody Rose. However, Yuki arrives just in time to stop him. At times, he would rather ignore his hunger to the point of starvation instead of going to Yuki for help. 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 towards 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 towards Purebloods because of their mechanisms in his life in particular, and because of this, he extends this hostility toward Yuki as well after she reawakens into a Pureblood vampire. In spite of this, his sense of duty overrides his issues, ensuring his reliability and trustworthiness.

A gifted hunter who is intelligent, athletic, and good-hearted, Zero nevertheless has a difficult time thinking of himself or any other vampire as anything but a monster. He struggles both with his desires for blood and in the latest chapters, his equally strong desire to kill vampires. Because of all this, Zero can be very closed off, as well as being difficult to understand or get close to, especially since he has a habit of not expressing his true feelings. He hides his true feelings behind a cold, composed personality. He has a lot of attitude, is not at all impressed or easily controlled by higher class vampires, and he also carries a positively burning hatred of all Purebloods. He often acts as if he doesn’t care about anything in order to hide all the scars and pain inside him that have nowhere to go. When not about his duties or in class, he can frequently be found in the Cross Academy stables with the fiery horse, White Lily, with whom he seems to share a special affinity. He is also quite a good cook which was admitted even by Aido, who is known for being quite picky.

History
Zero was born to a Vampire Hunter's family. Zero, along with his identical twin brother, Ichiru, and Kaito Takamiya, were trained as a vampire hunter by Toga Yagari who frequently looked after the twins when Zero's parents were out hunting. Yagari lost an eye protecting Zero when his teacher turned wild and tried attacking Zero due to her Level E state. His teacher had ran away a Pureblood vampire. This was Zero's first lesson on the danger of seemingly innocent vampires. Toga Yagari tells Zero that he will never regret losing his eye to protect him and Ichiru.

Four years ago, Zero and Ichiru found Shizuka Hio sitting in a tree, whom Zero immediately recognized as a vampire and told Ichiru to stay away from her. A few days later, Shizuka attacked his family. She bit Zero and killed his parents; Zero passed out believing she had killed his brother as well.

After that attack, Zero was taken in by Kaien Cross to stay in Cross Academy. Yuki approached him carefully and cared for him despite him being cold and hostile towards her. Zero gradually grew affection for her but kept it to himself due to her love for Kaname Kuran. Zero failed to reveal that he was going to turn into a vampire after Yuki said she was afraid of all other vampires. Over the next four years, the two become closer but not on a level they could call each other friends.

Plot
Main article: Plot Summary for Zero Kiryu

Powers and Abilities
Zero is a vampire hunter who was chosen by Kaname to become a Pureblood killing machine. Zero possesses the standard abilities to sense vampires from a far distance, accelerated healing and in spite of being a vampire, is also able to wield anti-vampire weapons, (But not artemis). Since he became a vampire, Zero is able to distinguish Purebloods from other vampires and has gained improved healing abilities. Kaname tells Zero that after he devours Ichiru's blood, he would become the world's strongest hunter. He then explains that since he has drank from Yuki's since she was a Pureblood, as well as Kaname and Shizuka's blood, it has made him the most powerful vampire hunter. After completing the fragment, along with Ichiru now being deceased, Bloody Rose has now become a part of his body, growing vines that can easily kill vampires; although it requires a high dosage of his blood to do so.

Zero's beast form made its first appearance in 40th Night after he drank Ichiru's blood and its shadow was seen on the wall. In 82nd Night, the beast form is released in a new attack from Bloody Rose when Zero fights Kaname shortly after drinking Sara Shirabuki's blood.

Bloody Rose
The Bloody Rose is an anti-vampire gun that Zero keeps behind his school uniform blazer. Zero is able to transform his gun, Bloody Rose into its evolved state, after consuming his twin brother, Ichiru. Bloody Rose literally becomes a part of his body. However the cost is using a high amount of his blood. In the manga and anime, Zero had used Bloody Rose to kill Rido. It is  Zero's main weapon throughout the entire series.

Origins of Bloody Rose
Bloody Rose was a weapon born from the sacrifice of a Pureblood vampire, The Hooded Woman, 10,000 years ago. Artemis and Bloody Rose were originally Kaname Kuran's personal weapons during the wartime before he gave them to Cross Kaien to be in-charge. They were later passed down to Yuki Kuran when she became the school guardian and Zero Kiryu when he became a vampire hunter respectively.

Yuki Kuran
Yuki Kuran and Zero Kiryu became friends after Zero was sent to live with Kaien Cross who became his adoptive father after the murder of his parents by the Pureblood vampire, Shizuka Hio. Both Zero and Yuki have a past with vampires making them both understand each other a little more than the other Day Class students. Whenever Zero has nightmares of the incident that day, Yuki would pat his head until he finally falls asleep. Though, Yuki was not aware of his growing feelings towards her except but her roommate & other only friend Sayori had noticed. Zero knows that Yuki has feelings for Kaname. Zero reveals his romantic feelings towards Yuki in 46th Night and even tells her that he only desires her blood. He asks her if the human Yuki he once knew is still inside her and after she replied that she was, he gives her a kiss goodbye. Letting her go to off to be with Kaname, he told her that when the next time they meet, he will kill her. She replied by saying she will be waiting for him.

Yuki decides she must hide the part of her heart that wants to mourn the loss of Zero. She wants to do what is best for Zero, and at the time that means she must run from him so that his has someone to chase after in order to live. Yuki later leaves with Kaname to the Kuran Mansion, and in a later chapter, she is seen telling Kaname that half of her heart belongs to Zero, showing that her thirst cannot be quenched by Kaname's blood alone.

Zero and Yuki have a complicated relationship. However, both continue to support each other no matter the circumstances. Yuki and Zero suppress the part of their hearts that want to tell the other their real feelings. Yuki and Zero both continue to protect each other, despite their opposite status as Pureblood Vampire and Vampire Hunter.

In the 87th Night, Zero relieves his feelings for Yuki at the masquerade ball and kisses her. The two recall the time they spent together and how dear their relationship is. Both Zero and Yuki wonder why they had to become enemies & and Yuki admits to herself that she does love him "I love him...this feeling is within me too." . When Kaname, their target, appears the two break apart and chase after him. As seen in 89th Night  Yuki erases Zero's memories for her grand plan of sacrificing her life to turn Kaname into a human. At the ending of 91st Night Zero drinks Yuki's blood and regains his memories of her. Before he hands her over to Aido, he comments that he had been afraid to face his true feelings, but not anymore. After gaining back his memories, he no longer feels hatred towards vampires like he once did and is seen to be standing next to Kaname in 92nd Night Zero told Kaname to fight alongside with him and face his feelings and not make Yuki cry anymore. Though its debatable as to whether or not *was never proven only that he had gotten over his hatred towards Purebloods & vampires* Zero forgives Kaname for causing the deaths of his parents and twin brother, and also for allowing him to become turned into a vampire.

Kaname, after throwing his heart into the furnace, embraces Yuki and Zero and tells them he wants the two childhood friends to become a couple. After that, Kaname "dies" and Yuki runs out to stop the fight between vampires and vampire hunters (only to have Artemis break before she's able to use it) Zero then appears and the two are shown somehow ending the feud once and for all. Then later on, we find Yuki in front of Kaname's ice coffin with Zero at her side. Zero embraces Yuki and tells her that Kaname's death isn't her fault and that she shouldn't feel guilty.

Zero asks Yuki to be with him, saying "I won’t run anymore. You too, it’s fine for you to take your time thinking about it. Because knowing you, you’re still blaming yourself anyway. Damn. Forget that. Say that you’ll be with me. No matter how many years it takes, no matter how many decades pass… till this hunger turns me to dust. Say it to me.”

Near Vampire Knight's end, Yuki is seen in front of a headstone with a broken piece of the Bloody Rose in her pocket. A thousand years has passed, and Zero Kiryu has passed away (due to not being a Pureblood only). Yuki talks to the headstone, a metaphorical representation of Zero, and thanks him for the happiness he has given her. Yuki then leaves the cemetery, a bright smile on her face, and heads to reawaken Kaname by sacrificing her life. She is repaying the debt she has to Kaname and granting him the human life he gave her as well as wanting to give him the happiness he gave to her. Kaname awakens as a human with Yuki's two children at his side, and is left to explore the human world without his memories as a vampire. It is revealed in the last chapter that Yuki had a daughter (with Kaname) and a son (with Zero).

Ichiru Kiryu
Ichiru was the younger twin brother of Zero. Since they were twins born to a Vampire Hunter family, Zero and Ichiru were the cursed twins. To Zero's discomfort, Ichiru often questioned in childhood why he was born since it was obvious that Zero was the one who should have eaten him in the womb. Zero would scold Ichiru for his self-loathing and try to comfort him. However, Ichiru's feelings of jealously and despair continued to grow until Shizuka appeared and offered him a means to escape his fate. Zero watched his twin in devastation as Ichiru ordered Shizuka to murder their parents and leave him to live. Now the hunter is torn between love and hate for his younger twin. Eventually it is learned that despite his conflicting feelings toward Ichiru he still loves his little brother. Before the war with Rido Kuran, Zero ate Ichiru (another meaning for taking in Ichiru Kiryu's blood so they would be one like how they were supposed to before they were born) Zero now has Ichiru's strength and skills inside him.

Shizuka Hio
The Pureblood, Shizuka Hio, became Zero's master after she bit him the night of the attack on his family. She claims she did it because Zero reminded her of her former lover, a level E vampire that his parents killed. Shizuka meets Zero again four years later at Cross Academy while hiding in her hostess body, Maria Kurenai. Despite concealing her presence, Zero recognizes her. During a confrontation with Shizuka, she begins to taunt him about being his master. Despite Zero's hatred for her strongly remained, he finds himself unable to go against her commands.

After watching Yuki getting threatened by Shizuka, he breaks away from her influence and manages to wound her. Shizuka escapes, but Zero is prevented from chasing her by a distraught Yuki, who'd previously realized that Zero had planned to sacrifice his life in order to kill Shizuka. Before allowing him to go, Yuki makes Zero promise to return after taking care of Shizuka. However, to Zero's shock, by the time he arrived to Shizuka, she has already been dealt the final blow by Kaname, who had been waiting for her in the wings. Though Kaname was the one who murdered Shizuka, Zero was blamed for her death by an angry vampire council.

Kaname Kuran
Zero disliked Kaname on sight recognizing him as a Pureblood vampire, like Shizuka Hio. Kaname has been his rival ever since. They are only tolerant of each other for the sake of Yuki Kuran. Zero's hatred towards Purebloods furthermore increases his hostility towards Kaname. By the end of the manga, both men have made amends to a certain extent.

Quotes

 * "They are beasts in human form!" (To Yuki)
 * "I feel like...I'll go mad ...if I'm not hunting vampires during the night." (To Yuki)
 * "They're beasts in human form! How can you trust them? Tell me!" (To Kaien)
 * "Are you going to let me live, Kuran?" (To Kaname)
 * "Drinking blood on school ground is prohibited. Perhaps you were drunk with the sweet smell of blood, Aido." (To Hanabusa)
 * "I am not your adopted son! You may have cared for me, but I did not allow you to ADOPT me!" (To Kaien)
 * "Don't talk about my parents like that!" (To Yagari)
 * " If you go one step ahead of me, I'll make you cry. " (To a Day Class Girl)
 * " Listen up, brats! Get the hell back to your dorms! Why do I have to deal with you running around screaming "Kyaa! Kyaa!" every damn day?! Why?! " (To the Day Class Girls)
 * "You'd probably wish to have your blood drank by Kaname-senpai, right? " ( To Yuki)
 * "You heard it too? The sound of your blood being sucked in by me. After such a hair-raising experience you can't act as if nothing has changed. So don't interfere anymore." (To Yuki) 
 * "Yuki, I...I only desired your blood, Yuki...I want it so much that it's unbearable to the point that unless I drank from you until the very limits of your life, I wouldn't be satisfied...such a disgusting, gluttonous greed...that is...the type of creature I am isn't it...?" (To Yuki)
 * "Ichiru told me to live... and fulfill my goal. But I was afraid..All this time...I haven't faced my true feelings. I won't hide behind excuses anymore." (To Yuki)

Trivia

 * Zero's given name (零) is usually read in Japanese as rei, which means zero. His surname, Kiryu, consists of the characters for auger (錐, kiri) and life (生, nama).
 * Zero's Japanese voice actor, Mamoru Miyano voiced Riku from the Kingdom Heart Series, an action rpg game series developed by Square Enix. Miyano also voiced Saruiko Fushimi from the K Project Series. He also voiced Tamaki Suoh from Ouran High School Host Club, Tokiya Ichinose from Uta no Prince sama and Light Yagami from Death Note.
 * Yuki, Zero, and Aido are the only characters whose seiyuu have also had roles in the Anime K Project Series.
 * Zero's English voice actor is Vic Mignogna, also voiced Edward Elric from the Fullmetal Alchemist anime as well as Yoshimori Sumimura from the Kekkaishi anime.
 * Coincidentally, all three characters have a parent(s) who is not present during a large part (or all) of the storyline. Zero's parents were killed, Yoshimori's mother is rarely home (to the point that other characters call her a bad mother) and Edward's father left him and his brother while they were children, with his mother dying soon after.
 * Coneticly both his Japanese and English voice actors who voiced Tamaki Suoh and Rin Matusaka
 * Curiously, Zero and Yuki's son has a great resemblance to Ichiru and Yuki. He is only a little taller than his older sister.
 * In the Anime, Ichiru stated that Zero's favourite meal is Vegetable Soup. However, In the Offical Fanbook, Ramen in Salt Broth is placed as Zero's favourite food.