39-year-old Ogata Satoko is a highly capable psychiatrist who is single. She's forthright, a caring older sister and reliable in her job and in private. Her interests are staying in luxurious Japanese inns and watching stand-up comedy videos.
Satoko hasn't had a boyfriend in the past five years. Nevertheless, she derives satisfaction from work and isn't worried about her finances. Among her good friends that she hangs out with are 35-year-old Morimura Nao, her junior who proclaims that she won't marry, and 39-year-old Oikawa Sadao, her peer since high school. Satoko is happily enjoying the single life.
At an alumni reunion as everyone is on the verge of 40, Takeuchi Mizue, her good friend since high school who is now a full-time housewife, rushes Satoko into action. "If you want children, you should marry now" and "It's women's happiness", but both are lost on Satoko, who isn't convinced.
One day, Satoko attempts to cheer up Nao, who is downcast over a shocking incident, and goes to her favourite hot-spring inn. There she coincidentally encounters a breakup between a handsome but somewhat odd man, Okamura Keitaro, and his girlfriend.