Kou Yamori

Kou Yamori (コウ) is the main protagonist of Call of the Night. He was an honorable student but he decided to drop out of school and now he desires to become a vampire, a task with which he enlists the help of Nazuna Nanakusa.

Appearance
Kou has a slender build and black eyes with small pupils and hair with a spiky profile. He usually wears black baggy shorts and a plain white shirt underneath a predominantly black jacket with a white stripe down either sleeve. He also wears a pair of white leather shoes for footwear.

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 and although he seems to have enjoyed a satisfying and successful life being honor student, that was a facade. School is not fun to him; he dislikes being the center of attention and isn't motivated enough to maintain his excellent school performance, finds it difficult to sympathize with the other students and doesn't understand the concept of love. He prefers to walk around at night, enjoying the freedom it provides, seeing becoming a vampire as the final form of that lifestyle. That goal was what made him feel a purpose for the first time in his life.

Despite getting grossed out and embarrassed by lewd topics, he is repeatedly shown displaying sexual attraction to others and subconsciously looks at big boobs. Anko says that, while he doesn't own adult magazines, he downloads certain pictures on his phone, regrets it and deletes them, only to repeat the process.

He's 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. Despite that, Kou can be very intelligent, picking up on things that others don't. Moreover, he has conversations with far more experienced and older people without any problems and is very compassionate, able to see the good in people even when they are his enemies.

Turning into a half-vampire changed Kou's personality to some extend, making him bloodthirsty like when he gleefully attacked Mahiru after the latter beat him up first, almost killing him before Nazuna interfered. He also became more assertive and intimidating and is also fed up with others, not holding back in verbal conversations.

Nazuna Nanakusa
Kou initially found Nazuna's personality to be weird and got grossed out and embarrassed because she frequently talked about lewd stuff, calling her a whore on multiple occasions. Despite their opposing personalities and not knowing what romantic love was in the first place, he chose to stay with her in order to become a vampire and didn't waver when other vampires offered to do the same for him. Kou felt jealous when she spent time with other guys and revealed that Kou was not her first (attempted) servant and grew more attached and also protective of Nazuna as time went on. He seems to have halfway fallen in love with her and the importance she has to him is shown when, in great distress, his mind revolved intensively around Nazuna.

Akira Asai
Kou and Akira knew each other since they were children and were what Kou would call "friends". They felt connected because of their similarities but he talked very little to Akira and was very reserved and passive towards her at the start. After entering 6th grade they stopped seeing each other. Kou remembered her as a very lively and talkative girl and was surprised by how gloomy she became. They would meet each other frequently from that point onward and enjoyed each others company. 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, it was Akira's words that made Kou come back to his senses and motivated him to move forward.

Mahiru Seki
Similar to Akira, Kou knew Mahiru since they were children, felt a unique connection with him and Akira and had his first proper conversation with Mahiru. Kou openly admired Mahiru from the start and was glad to talk to him. They would skip school together and Kou said that if he were to go to Hokkaido, he'd like to do so with Mahiru. As the years passed, Kou tried to imitate Mahiru's personality that made him so popular, not realizing that Mahiru was also faking his personality. After warning Mahiru that Kiku is dangerous, Mahiru beat him up which caused Kou to retaliate and intentionally try to hurt him, almost killing him. When Mahiru ended their friendship, Kou felt extreme guilt and became depressed but later came to the conclusion 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 go back 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 a relatively estranged relationship because of Kei's job that 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. Even though she is not very present in his life, he loves his mother and is actually glad that she raised him the way she did because he got to meet so many people and had a lot of fun.

Kiyosumi Shirakawa
Kou met her accidentally as Kiyosumi was Nazuna's customer and wanted to get a massage. As Nazuna was tired, 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 during the night. Because Kiyosumi could relate to him and started to cry because how much she hates her work environment, Kou realized that she had the same problem as him and felt the urge to save her, even forcefully preventing her from going back 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 (This section contains spoilers)

 * Half-vampire: Thanks to Nazuna sucking his blood, he can turn into a half-vampire. 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 half-vampire whenever he feels emotional pain and bleeds, like when Nazuna drank his blood and he saw some on his hands, and during his fight with Mahiru in which his nose bled. He later learns how to control it and activates it by piercing his ears.
 * Control of blood: An ability 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 own blood to such an extend that it's powerful enough to bring his severed arm back.

Quotes

 * (To Hatsuka) "Certainly, there's a huge gap between boys and girls. We can't understand each other. But if you think about it, it never had anything to do with gender. Until now, I've never been able to understand a single person. I can't understand Nazuna-chan nor can I understand you, Hatsuka-san. It doesn't have anything to do with men or women. Even if I was a girl, I'd still have tried to like Nazuna-chan, I think." -Chapter 45
 * (To Mahiru) "Release you? Hitting you once before that is fine, right?" -Chapter 103
 * (To Sakura) "Asakura-chan...didn't you say these ugly hoes are 'good girls'?" -Chapter 135
 * (To himself) "I'm fucking amazing..." -Chapter 135