Mahiro is Taichi's mother, yet his father was involved in an affair with her. Choosing the path of a single mother, Mahiro worked tirelessly to raise Taichi. In return, Taichi supported her by helping with household chores and never being selfish. However, her loneliness continued to grow day by day. When she graduated from university, Mahiro decided to use up her accumulated paid leave by taking Taichi with her for a belated summer vacation.