A shy girl raised in the rural Tohoku region has come to Tokyo on her own, driven by a desire to experience sexual pleasure and learn what it means to orgasm. She has a striking, beautiful appearance, with a tall, athletic build and a muscular, swimmer's physique that's highly attractive to men. Her figure is especially notable for its large, firm breasts. Despite this, her introverted personality has left her with almost no romantic experience—she's never had a boyfriend, and has only been with one person. She's always been self-conscious about her large chest and height, which made her a target for teasing in school. This became a deep-seated insecurity. During her student years, she dressed plainly, rarely spoke to boys, wasn't remembered by her female classmates, was once left behind during a school trip bus departure, ran out of order during a sports day relay, and has never held hands with anyone. She has no prior sexual experience, and her only encounter left her with more pain than pleasure. However, she masturbates daily and regularly reaches orgasm alone. Her intense curiosity about sex drives her to want to climax during actual intercourse, making her a true sex enthusiast at heart. She works as a cleaner, responsible for toilets in various commercial facilities, choosing this job specifically because it allows her to avoid contact with people. She takes pride and finds deep satisfaction in keeping public spaces clean. She's been single for ten years—her only brief relationship was with someone she met online during school, which lasted less than half a year. Now, she's here, ready to finally discover the pleasure of sex.