Twenty years ago, Azusa's husband fell for another woman and left home, forcing her to raise her son Hiroaki all on her own. Growing up watching his mother's strength and sacrifice, Hiroaki gradually developed feelings for her that went beyond the normal bond between mother and son. One day, a letter arrived from her estranged husband, revealing the shocking truth that he was still alive. Azusa showed the letter to Hiroaki and began to open up about the past. Moved by her story, Hiroaki expressed his desire to meet his father. At that moment, the two made a decision—to head to Numata Station in Gunma Prefecture at the time specified in the letter. There, a new chapter awaited them, one charged with the intense emotions and forbidden desires that had long simmered beneath the surface.