Aki, the stepmother, had been happily living with her husband and stepson Hiroshi, but when her husband went on a six-month business trip last year, she could no longer endure the loneliness and ended up committing a night of passion with her stepson. That momentary impulse did not remain isolated—it forged a new bond between them, growing deeper and shaking Hiroshi's sense of reason to its core. Even after her husband returned home, they could not bring their affair to an end. Their desires continue to spiral out of control, unfolding a shocking relationship that shatters the boundaries of normal family life.