Sumire Shiroshima is a current high school teacher who teaches art. Her figure is characterized by her voluptuous breasts and firm, shapely buttocks, forming an irresistibly seductive body that leaves people breathless. Students often jokingly refer to her as "big tits," and her physical appeal is widely acknowledged by those around her. Her father serves as the principal of a private high school, and having grown up in a strict household, she was under tight parental control until graduating from university—so much so that even dating men was forbidden. As a result, she had zero romantic or sexual experience, and only by becoming a teacher did she finally escape her father's watchful eye and gain freedom. However, this upbringing left her anxious and uncertain when it came to relationships with men. Eventually, she develops feelings for a married male colleague at work, leading to a physical relationship one day. The story's appeal lies in the progression of this affair and her inner emotional conflict.