Nao Saeki is happy with her life. She has a great job as a stylist, and also has a very sincere and loving fiancé, Kazuya Yuki. But one day, her sister Miho gets caught up in an incident overseas in which she is tragically killed. The shock of Miho's sudden death causes her husband Mitsuhiko to lose his memory. As a result of all that has taken place, Nao has to look after Mitsuhiko and his son Yusuke. At first, Nao is just trying to help the two. But living together and watching Mitsuhiko try to start a new life plants the seeds of a "new emotion" within her heart. It doesn't take long for those feelings to turn into love.
What Nao doesn't know is that her colleague Chihiro Tomita has feelings for Kazuya, as her own feelings waver back and forth between her brother-in-law and fiancé. When Mitsuhiko's memory comes back, the realization that he has lost his wife is more than he can bear - causing him great anguish. Later, Kazuya finds out about Nao's feelings for Mitsuhiko, and is torn by jealousy. And as the story reaches its final stage, we learn the real reason behind Miho's death.