Masaki's father disappeared shortly after his birth, leaving Reiko to raise her child alone. Touched by her relentless effort and devotion, Masaki gradually developed an intense sense of gratitude toward his mother. Over time, this gratitude deepened, and he began to see Reiko not just as a mother, but as a woman. Meanwhile, Reiko began to feel a deep emptiness inside the moment Masaki graduated from university. It was the loneliness of losing someone she loved—because their bond had long since evolved into a profound mutual love.