Natsu Kamijo is a homemaker living in an apartment with her husband Yoshiyuki and her children. One day, she hears a rumor that her friend Rie Komaki, who is also married, ran away with the other man. Natsu is quite surprised because she cares about her family the most. She gets a phone call from Rie herself, saying she has much more fulfilling life as "a woman." In the meantime, Yoshiyuki's young subordinate Ryu Saeki moves downstairs. Natsu begins to feel the stirrings in her mind.
