Kazumi Shimura is a 47-year-old housewife and the center of a family with four children. Her husband frequently stays away for long periods due to work, leaving her increasingly lonely. In that emotional void, she began a relationship with her younger son, suppressing her guilt while sensing a deep, irreversible change within herself. However, their secret was discovered by her older son, leading to an unexpected turn of events—because he too began desiring her. As the boundaries of family bonds and personal privacy blur, just how far will she go?