Shun Kaidō is a second-year student at PK Academy, standing 159 cm tall with a slender 45 kg build. He sports spiky silver or light-blue hair, striking red eyes, and signature red bandages wrapped around both arms. He claims these bandages seal his dark power, "Black Beat." His style features modified school uniforms with tattered collars and casual black clothing accented by gothic accessories outside school. Previously introverted and friendless before high school, he wore glasses with his hair covering his eyes. His encounter with upperclassman Mineo Nobuaki at PK Academy prompted a complete reinvention into a chuunibyou persona. He now believes he wields supernatural abilities as "The Jet-Black Wings" and that the world is controlled by the secret organization Dark Reunion. Despite these delusions, he demonstrates authentic bravery in crises, like instinctively shielding classmates, though his physical abilities are limited—he performs poorly in sports, fears water, and lacks directional sense. Academically proficient under his strict mother's influence, he nonetheless shows gaps in practical knowledge, such as confusing hair clinics with hospitals. His family includes a younger sister, Sora, and brother, Toki. Toki believes Shun's chuunibyou stories without question, often causing Shun embarrassment by repeating these tales publicly. Shun maintains an intricate internal mythology featuring seven distinct self-invented personalities, diagrammed in Chapter 221. These personas are his core identity ("Main Shun"), the destructive "Jin," the scheming "Mei," the timid "Ao," the conflicted "Suzaku," the supportive "Kai," and the gentle "Setsuna," all connected by rivalries and alliances. Initially isolated, he gradually forms friendships, most notably with Aren Kuboyasu, whom he addresses by first name—a sign of deep mutual trust. He joins the Occult Club, led by Kusuo Saiki, where his imaginative contributions find tacit acceptance. His relationship with Chiyo Yumehara evolves from her initial rating of him as "D+ boyfriend material" to one of mutual romantic interest, highlighted when he defends her from harassment. Key details include his October 3rd birthday, AB blood type, preference for salami, and the recurring theme song "Judgment Knights of Thunder" accompanying his heroic poses. His guardian spirit manifests as a chihuahua, and his aura resembles a chipmunk's.