Ousuke Kiryū has short black hair swept right across his face, dark brown eyes, and a distinctive mole below his left eye. Neglected by peers in childhood due to a heart condition limiting his physical abilities, he cultivated an acute skill in reading people as compensation. He intensely dislikes hospital food and prefers never to eat it again, while appreciating handcrafted items, particularly those crafted for him by girls. Socially, he maintains numerous friendships without gender discrimination and often acts as a group's moodmaker, though he interacts more easily with girls than forms deep bonds.

Bullying during his early years, stemming from physical frailty and breathing difficulties, fostered a pessimistic outlook on relationships and fear of abandonment. This isolation made him treasure his first genuine friendship with Asano, called Asa-chan, who accepted him without judgment. Despite this bond, insecurities about being left alone persisted, fueling emotional guardedness.

At Meiryou High School, koto became a significant outlet. His performance style mirrors his internal world—technically precise yet emotionally restrained—reflecting self-protective barriers and contrasting with performers channeling openness. His journey shows gradual emotional growth through sustained friendships and club participation, though his core fear of solitude remains an ongoing challenge.