Kazuki Hakei

"Before continuing on with a bunch of spoilers, you may want to read Kazuki Hakei's Origin Story."

Appearance
Kazuki is a slender teenager with green eyes and shoulder-length black hair, which he partially ties back in a messy ponytail most of the time; additionally, he has a mole under his left eye. His usual outfit consists of rather tight-fit, plain shirts and trousers, combined with a pair of well-worn, sturdy boots and occasionally a more loose-fit jacket.

Personality
Kazuki generally acts fairly unapproachable, quickly getting aggressive and snapping at people for seemingly no reason. He easily gets suspicious of others, and it takes quite some time until he lets his guard down and begins to genuinely trust new acquaintances, although he is extremely loyal once he is actually close with someone.

He tends to act on impulse rather than rational thinking, commonly running away from situations of conflict in an attempt at clearing his head and gaining some distance from the situation at hand.

While Kazuki does already have a somewhat hotheaded personality to begin with, a large part of his aggressive demeanor is a self-defense mechanism he developed after years of witnessing his parents' deteriorating relationship. To an extent, this also applies to the homophobic behavior he exhibits initially (since his father coming out as gay was what finally caused his parents to break up, leading Kazuki to blame him almost entirely for their problems). However, Kazuki is fully aware that he himself is also attracted to men, which he cannot quite admit to himself, thus trying to cover up his own shame and insecurity through snide remarks towards others. Because lying and dishonesty played a large role in his parents' relationship issues and, subsequently, his family falling apart, Kazuki strongly dislikes being lied to and is quick to detect signs of dishonesty in people's behavior / body language. After an event with a fellow student at his school in Psemata, he has also developed a hatred for vampires, largely rooted in the trauma of said event.

Abilities
Kazuki can move water at will. The more he controls at once, the more exhausted he becomes but it usually takes a while until that happens. As seen in his Origin Story, he can use it to shatter objects from the inside if there is enough water in it to do it, although he cannot do the same with human bodies. He is currently trying to learn to walk on water, but it proves to be difficult.

Eitarou Hakei
During his childhood, Kazuki is very attached to his father Eitarou and looks up to him as a major role model, which still continues even as the arguments between his parents become more frequent and he grows more aware of them. However, when Kazuki finds out about Eitarou having an affair with another man behind his mother’s back, this changes drastically, with Kazuki resenting his father for the lies he had told, and holding on to this grudge for years. After running away from home, Kazuki ignores any attempts Eitarou makes to reach out to him; their relationship only improves again when Sora initiates contact between them and Eitarou gets an opportunity to apologize. While Kazuki still subconsciously blames Eitarou for a lot of his own issues and it's questionable if he will ever forgive him entirely, they do eventually communicate more regularly again.

Miharu Hirota
Miharu is Kazuki's friend and classmate from his hometown Psemata. Despite occasional conflicts, he feels at ease around her, with her being essentially the only constant source of support in his home life, and they stay in touch through letters even after Kazuki runs away from home.

Dolion Angelos
Dolion is an upperclassman from Kazuki's school in Psemata. Kazuki liked him at first, viewing him as support to help with his family situation and even feeling romantically attracted to him to a degree. After Dolion reveals himself to be a vampire, this changes entirely, and the incident plays a large role both in Kazuki's dislike for being lied to and his decision to leave his hometown, while also contributing immensely to Kazuki's later homophobic behavior. Traumatized by Dolion's betrayal, Kazuki still feels wary of anyone who might be a vampire to this day, although he himself might not consciously make that connection.

Akihiro Belial
Kazuki does not seem to like Akihiro. This is due to a subconscious comparison between his father that he perceives as weak and a bootlicker and Akihiro, who seems to be submissive towards Einstein with whatever he does. Additionally, Kazuki thinks that Akihiro is too uptight and strict with his oftentimes needless and unnecessary rules.

Sora Zaniah
Initially, Kazuki doesn't particularly care about Sora, although he unintentionally intimidates him with his rather unapproachable, snappy attitude. However, as they spend more time together, they gradually get closer, with Sora's gentle, supportive personality being a good counterpart to Kazuki's own harsh behavior. Kazuki is noticeably comfortable with Sora, to a degree where he actually begins to feel at least a bit less insecure about his orientation and romantic preferences.

Jade
Jade and Kazuki became great friends rather quickly. At the beginning, the latter was still skeptical, sensing that something was off about Jade, but that feeling went away the more time they spent time together. When Jade was revealed as a vampire and spy of the opposing kingdom, Kazuki felt betrayed and lied to. It took several months and Jade trying to convince him repeatedly that his feelings and their friendship were not a lie to mend their relationship. Now, they are mostly back to normal, both of them pushing the other to improve themselves. They love to torment Akihiro together, being usually the ones to do the things they are not supposed to do together and go against anything Akihiro tells them. Despite not being the type to openly joke around and show anything other than annoyance like Jade is, they still get along great and even complete each other in that aspect.

Trivia

 * His last name Hakei (波形) can mean "wave shape" or "ripple mark".