Shun Kaidō defines himself through a unique physical appearance and crafted persona at PK Academy. Standing 159 cm tall, he is the shortest male in his class, sporting spiky light blue hair and red eyes. He wears red bandages on both arms, claiming they seal a dangerous power called "Dark Beat" within his right arm. This aesthetic extends to his modified school uniform, featuring a tattered collar and intentional tears; his casual wear consistently covers his arms. He transformed from a shy, glasses-wearing middle schooler with hair obscuring his face into this current look upon entering high school, aiming to attract friends. His personality centers on chuunibyou syndrome, manifesting in the alter ego "The Jet-Black Wings." He frequently declares that an evil organization, Dark Reunion, controls the world and claims supernatural abilities to fight them. Despite grandiose proclamations, he is physically weak, struggles with sports, and cannot swim. Academically, he achieves high grades under strict parental enforcement, yet displays gaps in practical knowledge—mistaking hair clinics for hospitals—and lacks skills in sketching or map navigation. He displays flashes of impulsive bravery, like intercepting a snake lunging at a classmate, though often requires rescue afterward. Attention-seeking behavior sometimes leads to social missteps, such as falsely claiming credit near influential individuals. His background reveals past isolation; he had no friends in middle school. He reinvented himself at PK Academy after learning about chuunibyou from classmate Mineo Nobuaki. He sought friendship with Kusuo Saiki, mistakenly believing he witnessed Saiki teleporting and perceiving him as a fellow outcast, a desire stemming from loneliness. His home life involves an overbearing mother who infantilizes him (calling him "Shun Baby") and pressures him academically. He has two younger siblings: Toki, who believes his heroic stories, and Sora. Outside school, he briefly worked as a waiter and fell victim to repeated scams fueled by his Dark Reunion paranoia, both resolved through Saiki's indirect help. Relationships shape his development. He considers Saiki a close ally despite Saiki's reluctance, and Kuboyasu Aren is the only non-family member who addresses him by his first name. He demonstrates loyalty, valuing others' present character over their past. His delusions occasionally influence peers, like when scammers adopted his paranoia after Saiki's interventions. Recurring elements include his self-composed theme song "Judgment Knights of Thunder" playing during attempted heroics and a chihuahua guardian spirit reflecting his perceived fragility. Trivia notes include his name deriving from the Japanese term for teleportation ("shunkan idō"), his favorite food being salami, and his character song "Bloody Moon" performed in an anime episode. His aura resembles a chipmunk's, aligning with his skittish yet earnest demeanor. Despite ongoing delusions, core traits persist: a longing for connection masked by bravado and spontaneous protectiveness.