Five years ago, Yuriko lost her husband in a landslide accident at a dam construction site. While still wrapped in deep sorrow, her bond with her son Taichi gradually grew stronger. Before long, their relationship evolved into something beyond mother and son, and they began having sex constantly, day and night. Yet every year on the anniversary of her husband's death, she visits the dam to lay flowers, unable to forget that tragic day. She trembles with guilt and taboo, wondering what her late husband would think if he knew about their relationship—but she remains unable to sever the bond she shares with Taichi.