Kazune Kujyou is one of the central characters and the primary male protagonist. He is a student in the seventh grade and is initially presented as a cool, dependable, and academically gifted individual who also excels in archery and various martial arts. Because of his abilities and appearance, he has a significant following at school, known as the Kazune-Z fan club. However, this composed exterior hides a more complex personality. While he often speaks to the main character, Karin Hanazono, in a manner she and others consider sexist, making broad statements about the perceived weakness or lack of intelligence in girls, this is a facade that covers a deeply caring nature. Kazune also possesses a notable and intense fear of bugs, a phobia that starkly contrasts with his otherwise fearless demeanor.

His background is a central element of the story's mystery. He lives with his cousin, Himeka Kujyou, but their family situation is far from ordinary. Kazune is revealed to be an incomplete clone of the man he calls his father, Professor Kazuto Kujyou. This knowledge has given him a complex about being a copy or artificial. The fact that he is an incomplete clone has serious physical consequences; his body cannot fully handle the power of his transformation, causing him to collapse or pass out after he uses his godly abilities. He is also required to take medication to manage his condition. Despite his outwardly cool and sometimes aloof behavior, particularly in the present, Himeka recalls that he was weak and frequently cried when he was younger, and that his personality shifted to become more confident around the age of ten.

Kazune's primary motivation is the protection of his loved ones, especially Himeka. His role in the story is that of a guide and guardian to Karin, who discovers she can harness the power of a goddess. He introduces her to this hidden magical conflict but frequently finds himself needing to protect her, especially when her reckless or impulsive nature leads her into danger. His feelings towards Karin evolve significantly over the course of the narrative. Initially, their relationship is antagonistic, defined by his teasing and her frustration with him. However, he eventually falls in love with her. This is complicated by the fact that he has known since he was ten years old that Karin is actually the de-aged reincarnation of Suzuka, the wife of his genetic template, Kazuto, and the mother of Himeka. This makes Karin, in a sense, his mother, adding a profound and unusual layer to their romantic relationship. His key relationships also include his cousin Himeka, whom he is fiercely protective of, and Michiru Nishikiori, a friend and fellow ring-user.

Kazune undergoes a notable development from a seemingly perfect but emotionally closed-off boy to someone more vulnerable and open about his feelings. His fear of being a copy or a failure is a recurring internal conflict that he must overcome. In some storylines, particularly in the sequel, his fate is tragic; it is revealed that in an alternate future timeline, he dies from the strain of his battles, and Karin lies to their son, telling him that Kazune abandoned them rather than reveal the truth of his sacrifice. This highlights his dedication to protecting others, even at the ultimate cost. In terms of abilities, Kazune possesses a ring that allows him to transform into a god. In the original series, his divine power is that of Apollo, the Greek god of the sun, and his primary weapon in this form is a bow and arrow. In the sequel series, Kamichama Karin Chu, his power changes to that of Uranus. His god form is incomplete, which is the direct cause of his post-transformation collapses. He also has the ability to speak to his cat, Nyake.