Sumire grew up in a wealthy household and attended a prestigious girls' school, raised as a sheltered daughter. Despite her protected upbringing, she had been interested in boys since her youth. She lost her virginity in her first year of high school, and by the time she graduated from university, she had dated over ten men. She married through an arranged match to a man five years her senior who worked at a top-tier company. However, due to her husband's unexciting sex life, she began seeking other men who wouldn't significantly impact her family life. She once had a dominant older boyfriend, but after giving birth to her child, she stopped contacting him for a long time.