Shun Kaidou exhibits classic signs of chuunibyou, a condition associated with adolescents who harbor grandiose delusions and act as if they possess supernatural powers. During middle school, Shun was shy and friendless. Upon entering PK Academy, he attempted to reinvent himself as a more confident and adult-like individual, but this effort evolved into his current eccentric persona. He adopted the alias The Jet-Black Wings and frequently claims to be targeted by a shadowy organization known as the Dark Reunion, which he believes manipulates world events. These exaggerated claims are intended to impress his peers and make him appear cool, though they often lead to embarrassment or trouble.

Despite his overconfidence, Shun is physically weak, lacks athletic ability, and cannot swim. He often places himself in dangerous or awkward situations due to his delusions, such as when he boasts to his younger brother Toki about controlling their neighborhood, only for Toki to repeat the claim to a nearby thug, causing Shun to panic. Similarly, he once attempted to take credit for leading a protest against Metori Saiko, unaware that Saiko was within earshot.

Shun’s delusions run so deep that he begins to believe his own invented lore about The Jet-Black Wings. He frequently tries to impress his classmates especially Kusuo Saiki but often ends up humiliating himself. Nevertheless, in private or when under stress (such as around his strict and overbearing mother), Shun drops the act and behaves more like a typical, awkward teenager.

Academically, Shun is a capable student, largely due to his mother’s insistence on academic excellence. He maintains good grades, though his intelligence is not particularly well-rounded. He is poor at sketching, struggles with map reading, and once mistook a hair clinic for a hospital. He is also impulsive and occasionally shows reckless bravery most notably when he threw himself in front of a lunging snake to protect a classmate, acting without thinking of the consequences until it was too late. In that moment, Kusuo had to intervene to save him.

Despite his flaws and eccentricities, Shun is earnest and well-meaning, and his loyalty to his small circle of friends remains unwavering.

In middle school, Shun Kaidou had a withdrawn and nerdy appearance. He wore his hair down with bangs covering his face and glasses, embodying a shy and reserved persona. Upon entering high school, he drastically changed his appearance in an attempt to reinvent himself and make friends. He now styles his hair in upward spikes and wears contact lenses instead of glasses.

As a reflection of his chuunibyou delusions, Shun wears red bandages around both arms, which he claims are used to seal away his hidden powers. These bandages are worn consistently, both in and out of school, and resemble the wrappings of a boxer or martial artist. He is the shortest male student in his class standing shorter than many of the female students as well.

At PK Academy, Shun wears the standard male uniform, but in a tattered and stylized form to match his exaggerated persona. His collar is frayed, and parts of the uniform are torn for dramatic effect. On days off, he dresses casually, though his arms remain covered either by long sleeves or his signature red bandages.

Shun Kaidou spent his early years as a shy and introverted student, often labeled as a “nerd” by his peers. Wanting to change his image and gain friends, he decided to reinvent himself upon entering high school. During his freshman year at PK Academy, he met Mineo Nobuaki, who introduced him to the concept of chuunibyou, a delusional behavior in which one pretends to have secret powers and enemies. Inspired by this, Shun adopted the persona of The Jet-Black Wings and began crafting elaborate fantasies about battling the evil organization known as The Dark Reunion.

Shun eventually crossed paths with Kusuo Saiki, whom he suspected to be special as well. While Kusuo initially tried to avoid him, he reluctantly began interacting with Shun after realizing that he had seen him teleport near his neighborhood. Though it was later revealed that Shun hadn’t actually seen Kusuo’s face clearly during the incident, the encounter became the catalyst for their friendship. Shun, feeling like an outcast himself, was drawn to Kusuo and sought to form a bond with someone he believed to be another outsider. Over time, their friendship developed despite Kusuo’s continual attempts to maintain distance.