Kou Yamori

"I've just been taking walks at night recently that's all." "Ahhh... Have you?" "Yeah. I made a lot of good friends, the kind I never would've made normally... I really like them all too. So I've been having a lot of fun these days. I've had my share of problems, but I'm sure they will all work out. So I'm not worried at all. If you weren't doing what you're doing now, I never would've been able to meet them. So I'm actually thankful I was raised the way I was."

- Kou Yamori and Kei Yamori

Kou Yamori (コウ) is a middle school student who began skipping classes to venture around his home city at late night. Since he first began roaming around, Kou befriended Nazuna Nanakusa, a vampire who he intended to develop romantic feelings for in order to be able to be turned into a vampire by her. His close time with Nazuna caught the attention of a group of vampires, led by Nico Hirata, who confirmed that Kou would be assassinated if he were not to become a vampire within a year. However, Kou and Nazuna succeeded in befriending each of them within a couple of months. Throughout his insomnia nights, he had came across more friends he had ever had before, and eventually, Yamori encountered Anko Uguisu, a detective who sought to eliminate all vampires.

Kou and Nazuna grew closer to each other as friends, and they went up against Uguisu's campaign in order to save their allies. After discovering the detective's true identity as Kyouko Mejiro, Kou and Nazuna clashed with her during halloween, and when Kyouko/Anko attempted to commit suicide, Kou prevented her from doing so, which ultimately allowed his Half-Vampire self, a hybrid between humans and vampires, to surface. Coming to good terms with the reformed Anko, the three of them began investigating the nature of his half-vampire state, and during the process, Kou had a brutal fallout with his friend, Mahiru Seki, who had been acquainted with Kiku Hoshimi. In search of Seki to reconcile, Kou, along with his new friends, chased after Kiku and joined a school trip to Hokkaido, where Kou was almost murdered by Kiku before making amends with Mahiru.

Appearance
Kou has a slender and relatively short build. He has eyes with small pupils featuring eye bags. Despite usually being portrayed as black, Kou's eyes sometimes appear to be amber-colored. He has short black hair with a spiky profile. He usually wears black baggy shorts and a white t-shirt underneath a predominantly black jacket with a white stripe down each sleeve. He also wears a pair of white leather shoes for footwear. Later on, he is seen with an earring on his left ear. After his jacket gets damaged, he replaces it with another one that looks almost identical but has two slightly different white stripes on its sleeves.

Kou's school uniform consists of a grey suit with a white shirt, a striped tie underneath, grey pants, and a wide black belt. On the school trip, he still wears his casual clothes despite Hokkaido's harsh climate, claiming he is not bothered by it because he wears Heattech underneath. That claim is questionable, as he still wears shorts, exposing his legs to the cold.

Personality
Kou is a gloomy and reserved boy who has been that way since early childhood. After entering middle school, he was friendly, upbeat, and a showcase student. Although he seems to have enjoyed a satisfying and successful life being an honor student, that was a facade. Despite being proud of his popularity, Kou doesn't have fun at school. He isn't motivated enough to maintain his excellent school performance, cannot relate to other people, and doesn't understand the concept of love. He prefers to walk around at night, enjoying the freedom it provides, and sees becoming a vampire as the last step that will make him able to live that lifestyle for eternity. That goal made him feel a purpose for the first time ever.

Kou has a strong sense of justice that he is very vocal about, and he is quick to scold someone whom he perceives as amoral. However, his morals can be unusual; he doesn't think killing someone is inherently wrong, as sometimes one has no other choice. Seri Kikyou describes him as someone who values the lives of his friends above those of others.

He is confused about his own emotions and doesn't know what it feels like to like someone in a romantic sense. Despite claiming not to mind loneliness and having acted indifferent towards others when he was younger, Kou yearns for contact with other people. That was shown when he put a walkie-talkie on a postbox in the past, hoping that a random person would find it.

As the story progresses, Kou undergoes noticeable emotional growth. He opens up more, shows more emotion, becomes more determined to reach his goals, is more confident, and is more lively in general. Kou has also become fed up with others, not holding back in verbal conversations.

Despite getting grossed out and embarrassed by lewd topics, he is repeatedly shown to be quite lecherous and subconsciously stares at big breasts. Anko Uguisu says that, while he doesn't own adult magazines, he downloads specific pictures on his phone, regrets doing it, and deletes them, only to repeat the process.

Kou is mature for his age and doesn't seem to be afraid of many things; for example, he roams the nights alone as a 14-year-old without much fear and gets involved with vampires without further doubt, making Akira doubt his intelligence. However, Kou can be very intelligent, picking up on things that others don't and often able to see past other people's lies. Moreover, he has conversations with far more experienced and older people without any problems. Kou is very compassionate and tries to see the good in people even when they are enemies. He puts a lot of trust in others and can give people too much credit, making him vulnerable to deception.

After he turns into a half-vampire, Kou's personality changes drastically, making him bloodthirsty and unhinged, like when he gleefully attacked Mahiru after the latter beat him up first, almost killing him before Nazuna interfered. Though, his intent was only to punch and hurt Mahiru. The transformation also affects his personality in his human state. He has become more prone to anger, more assertive, and more intimidating. However, that hasn't erased his old self.

Family

 * Father
 * Kei Yamori - Mother

Allies

 * Akira Asai - Classmate and Friend
 * Mahiru Seki - Former Classmate and Former Friend
 * Saki Fujiwara
 * Michiko
 * Nazuna Nanakusa - Best Friend, Savior and Girlfriend
 * Seri Kikiyou - Former Attempted Killer and Friend
 * Akihito Akiyama - Friend
 * Kabura Honda - Former Kidnapper and Friend
 * Nico Hirata - Temporary Enemy, Former Teacher and Friend
 * Midori Kohakobe - Temporary Enemy and Friend
 * Hatsuka Suzushiro - Temporary Enemy and Friend
 * Kiku Hoshimi - Former Attempted Killer
 * Lira Echigo - Ex-Girlfriend
 * Kyouko Mejiro - Former Enemy and Friend
 * Azami - Temporary Enemy, Friend and Savior
 * Susuki - Temporary Enemy and Friend
 * Haruka Nanakusa - Temporary Enemy, Rival and Savior

Enemies

 * Michihisa Kanou †

Nazuna Nanakusa


Kou initially found Nazuna's personality to be weird and got grossed out and embarrassed because she frequently talked about lewd topics, calling her a whore on multiple occasions. Yet despite her not being his type, he also described her presence as "not uncomfortable." After Nazuna kissed him for the first time, his heart was beating, and he believed himself to have fallen in love, unaware that he was feeling lust. Even though he denied it, Kou wanted her to kiss him again.

Despite their opposing personalities and not knowing what romantic love was in the first place, he chose to stay with her to become a vampire and didn't waver when other vampires offered to do the same for him. In fact, despite Nazuna's personality being unappealing to many, Kou preferred her over the other vampires whose overly girly personalities made him uncomfortable and told her he was glad that she was the one he met first.

Kou told Nazuna that he was always bored until he met her, and after knowing the meeting was mutual, he proposed they search for new things and have fun together. Kou becomes jealous when Nazuna gets intimate with others, like when she flirts with men at a pool party and reveals that he was not her first (attempted) servant. As time passed, he grew more attached and protective of Nazuna and now seems to have halfway fallen in love with her. Her importance to him was shown when, in great distress, his mind revolved intensively around Nazuna.

Akira Asai


Kou and Akira had known each other since they were children and were what Kou would call "friends." Still, he talked very little to Akira, was very reserved and passive towards her at the start, and had no problem leaving her alone since she was popular among her peers. Kou was unaware that he was the only one Akira genuinely saw as a friend at the time and only learned her room number years later. After entering 6th grade, they stopped seeing each other.

Kou remembered her as an energetic and talkative girl and was surprised by how gloomy she became. They would frequently meet from that point onward and enjoyed each other's company. Kou took his friendship with her more seriously than before and opened up to her about why he quit school and wanted to become a vampire. While he accepts her offer to suck her blood once he becomes a vampire, he doesn't want her to fall in love with him. After he fell into depression and not even Nazuna could help him, Akira's words made Kou come back to his senses and motivated him to move forward.

Mahiru Seki


Like Akira, Kou knew Mahiru since they were children, felt a unique connection with him and Akira, and had his first proper conversation with Mahiru. Despite his reserved nature at the time, Kou liked to spend time with Mahiru and didn't go on a school trip because Mahiru wasn't going. On that day, the two enjoyed each other's company and had lots of fun. Kou eventually told Mahiru that, since he wanted to, he should go to Hokkaido, no matter what his family said. Kou openly admired Mahiru from the start. As the years passed, he tried to imitate Mahiru's personality, which made him so popular, not realizing that Mahiru was also faking his personality.

After warning Mahiru that Kiku is dangerous, Mahiru beats him up, which causes Kou to retaliate and intentionally try to hurt him, almost killing him. After Mahiru ended their friendship, Kou felt extreme guilt and became depressed but eventually concluded that he didn't do anything wrong, even planning on making Mahiru apologize to him instead. He wants to make up with Mahiru but doesn't want to force him to return to his old life and is willing to accept Mahiru rejecting him, but only if that's his genuine desire and not a product of Kiku's deception. Currently, Kou is searching for Mahiru in Hokkaido.

Kei Yamori
The two have an estranged relationship because Kei's job doesn't let her spend much time with Kou. Kou doesn't seem to know her very well, believing that she would not allow him to go out at night despite Kei not minding, and didn't trust her much initially, remarking that he had no person he could trust at the start of the story. He also asked himself whether he ever got coddled by his mother.

After Kei confronted Kou about not going to school, he explained why he quit and was surprised by how relaxed Kei was about his lifestyle. Even though she is not very present in his life, he loves his mother. After Kei called herself a bad mother, Kou told her about the new friends he met and the fun he had. He explained that he was glad she raised him the way she did because those things would have never happened otherwise.

Kiyosumi Shirakawa
Kou met her accidentally as Kiyosumi was Nazuna's customer and wanted to get a massage. Nazuna was tired, so he was forced to give her the massage, which he hesitantly accepted. Kou would tell her about himself and why he likes to go outside at night. He realized she had the same problem as him when Kiyosumi could relate to him and started crying because she hated her work environment. He felt the urge to save her and even forcefully prevented her from returning to work. He then revealed to her his goal of becoming a vampire with the help of Nazuna and promised to turn her into a vampire one day as well.

Abilities

 * Half-vampire: Thanks to Nazuna sucking his blood, he can turn into a vampire for a limited amount of time. While the full extent of his abilities isn't clear, it has shown to give him the powers of a vampire and, depending on his emotional state, amplify them, making him able to destroy a building with one punch, even overwhelming a particularly strong and experienced vampire like Susuki. He couldn't initially control the ability, but it's shown that he turns into a vampire whenever he feels pain and bleeds, like when he saw his blood on his hands after Nazuna drank it and during his fight with Mahiru in which his nose bled. He later learns how to control the ability and activates it by piercing his ears.


 * Control of blood: An ability that is unknown even to vampires. When Kou's arm was severed, his vampiric side intensified as his mind revolved more and more around Nazuna. He can control his blood to such an extent that it's powerful enough to bring his severed arm back.

Trivia

 * Despite usually getting portrayed with black eyes, Kou and Akira also got drawn with amber eyes by Kotoyama. In Kou's case, it was on the covers of volume 3 and 11.
 * Kou's blood is said to be extraordinarily delicious for vampires.
 * Kou mentions that he would have tried to fall in love with Nazuna even if he was female, indicating Kou to be potentially pan or demiromantic.
 * Kou has never been at sea in his life.
 * His birthday was revealed in the official fanbook.
 * Kou owns several track jackets.
 * Kou's type of eyes is called Sanpaku eyes (三白眼). While such eyes are more of a simple design choice in fiction, there is a belief in Japan that they indicate the person is either in danger or has violent and psychotic tendencies. The latter becomes true in Kou's case as the story goes on.

Quotes

 * (To Nazuna) "Miss vampire! I have one wish. Make me a vampire."
 * (To Mahiru) "Release you? Hitting you back once before that is fine, right?"
 * (To Sakura) "Asakura-chan...didn't you say these ugly hoes are 'good girls'?"
 * (To himself) "I'm fucking amazing..."