Ami Hirabayashi, an office lady who works for a trading company, was spending a little nervous days ahead of her 30th birthday. She has a lover, Keiichi Haraguchi, who is three years younger than her, but her relationship is kept secret around her. She's about to get married, but she doesn't seem to propose to Keiichi. Ami, who has a sober personality, doesn't mind that Keiichi, who is good-looking and good at spoiling, is being targeted by the women around her. She always thinks negative things, "She will be thrown away someday." One day, the two of them played a big game ...