Nurse Rena Momokawa devotedly cares for her ailing father-in-law, tirelessly tending to him as his condition worsens. When he accidentally sees her underwear, he becomes intensely aroused. Though he tries to restrain himself, his desire for Rena grows uncontrollable. One day, while she is wiping his body, he exposes his erect cock and pressures her, but she resists and manages to escape the situation. However, that night, imagining his powerful manhood, Rena can no longer suppress her urges and begins pleasuring herself. Eventually, she gives in to his advances and surrenders her body, engaging in repeated acts of adultery. Each encounter brings her pleasure—but steadily drains her father-in-law's failing life force.