Ai-chan is a second-year high school student who stands 149 centimeters tall and weighs 50 kilograms. She has brown hair styled in a bob cut with two braided strands behind her ears, blue eyes, and a curvy figure that draws persistent attention. Her large bust, which grows over time, is a source of self-consciousness as her height remains unchanged. At home she sometimes wears glasses, though she no longer uses them regularly as she did in middle school. At school, she is reserved and introverted, often reading alone or rejecting confessions due to unwanted attention and peer jealousy. Around trusted individuals such as the Salaryman she befriends, she reveals a playful, mischievous side and a wide emotional range. Their bond began during a crowded Monday morning train commute when he accidentally dropped his business card on her; after an awkward encounter that led to his brief hospitalization, they developed a recurring Monday ritual where he acts as her bodyguard on the train. She gives him buttons popped from her shirts by her bust size as symbols of their connection. She works a part-time job at Bakery Restaurant Tawawa despite school prohibitions, wearing a uniform that strains against her figure, and she invites him to visit. She expresses aspirations to study nursing. Ai-chan lives with her mother, who frequently mends clothing damaged by their figures, and a younger sister who shares similar traits; she is calmer and more polite compared to her sister. Her protective best friend, Volley-bu-chan, teases her about her appearance. Ai-chan can be possessive and shows discomfort with the Salaryman’s interest in other women; after accidentally breaking an adult video in his apartment, she attempts to apologize by wearing her work uniform for him, insisting he focus solely on her. She was born on October 5, has AB blood type, favors the color indigo and soy milk as a food, relieves stress by eating, struggles in mathematics and physical education, and prefers honest romantic partners without secrets.