Before his fourth birthday, Kou is kidnapped, leaving his mother Yui devastated. Divorced and living alone, Yui's world is suddenly shaken when she receives a call that Kou has been found.

Through a series of phone calls with Kou, Yui begins to perk up. Meanwhile, Kino, a child welfare worker, visits Yoichi, Kou's father, and confides in him that Kou has been found and that Kou has a letter containing a shocking fact.

Yui and Yoichi come to an agreement to live with Kou. As they begin to forge a new life together as a family, Kou secretly remains in contact with Asako.

Upon realizing that Kou is actively avoiding her, Yui does not know what to do with Kou and keeps it to herself.

On his way back to the orphanage, Kou vanishes, causing Yui to grow concerned that he may have gone back to Asako's. Meanwhile, Asako receives a job offer from Kotone.

Yui discovers Asako's heart-wrenching past and learns the truth about her meeting with Kou, a truth that is far worse than Yui ever imagined.