It has been a year since Misako became Yosuke Amamiya's wife, yet her new stepson Kazuhiko still barely acknowledges her, let alone views her as a mother figure. However, a more urgent concern occupies her mind: when she is home alone, she frequently receives threatening calls from a stranger who possesses detailed knowledge of her daily routine. Unable to discuss this with Yosuke, she keeps these disturbing interactions to herself. Just as Kazuhiko begins to warm up to Misako, the situation takes a darker turn when a sex toy is delivered to her door. Left unsatisfied by her workaholic husband, she starts a new habit: masturbating while on the phone with the unknown caller. One day, Misako realizes she is not the only one hiding a dirty secret when she catches Kazuhiko pleasuring himself with her underwear! Now aware that her stepson sees her as a woman, where will all this sexual tension lead?