Shigeru has become physically weakened and requires care, living with his son Toshifumi and daughter-in-law Tamae. Once full of energy, Shigeru grows increasingly depressed due to his physical limitations—until one day, he accidentally witnesses his son and daughter-in-law having sex. In that moment, he realizes his own body has become aroused. Pretending to be frail, Shigeru begins initiating erotic advances. Sensing his desire, Tamae finds herself unable to resist. As Shigeru's hidden lust intertwines with the couple's daily life, a forbidden relationship begins to unfold.