Ten years ago, Emiko divorced her husband and raised her son Tatsuya alone. Now that Tatsuya has finally secured a job and is planning to live on his own starting next April, she feels a bittersweet sense of accomplishment. One day, Tatsuya invites her on a hot spring graduation trip, and they embark on a private journey together. At their destination, he suddenly confesses, "Mom, thank you. I've always loved you..." His words shake Emiko to her core. By the end of this trip, the thought of living apart becomes unbearable. Amid an atmosphere thick with warmth and sweetness, a real mother and son cross the line into a forbidden relationship...