Mayu is a very kind, shy girl. Kohta and Yuka meet her just a day before her 14th birthday, and soon learn that she is
homeless. Though they never know it, Mayu was sexually abused/raped by her step father and ran away when her mother neglected
to care. Mayu finds a dog (who she names Wanta) and befriends him.
One day, a lady takes Wanta away, and calls him "James", saying that he is her lost dog. Wanta mysteriously returns...
(that's never really explained).
Kohta and Yuka adopt Mayu and send her to school. This forms the beginning of their "family".