Kohhei, the grandson, lives surrounded by his always kind grandmother, Mitsue. He deeply cherishes the warm moments they share and is genuinely grateful for her kindness. Seeking opportunities to bathe together, he starts with the simple act of washing her back, gradually deepening their bond. Amid the steam and commotion of the bath, he begins touching his grandmother's body, drawn to her warmth. Eventually, he forces himself on her, coercing her into sex. Thus begins their forbidden relationship. A twisted tale of illicit love and incest unfolds between grandson and grandmother.