父親の再婚によって美人の義母と義妹ができた直人。だが義妹である優衣との距離感を測りかねる日々が続いていることに不安を感じていた。ある日ふと手元の携帯を見ると、相手のことがなんでも分かるという不思議なアプリが。さっそく妹にアプリを使用すると、なんと妹の身体に乗り移ってしまった。困惑しつつも妹の部屋へ戻るが、姿見に映った妹の身体に日頃抑えていた劣情が噴出。欲情を抑えられなくなりハリのある胸やぷっくりと膨らんだ乳首を触り、未体験の女の快感を楽しんでいくのであった。
Naoto is an ordinary guy who, after his mother's death and his father's remarriage, has two beautiful women enter his life–Sachiko, his stepmother, and Yui, his stepsister. However, as the days go by, Naoto begins to worry about Yui's emotional distance from him. One day, he glances at his phone to find a miraculous app that promises to aid its user in understanding the person of their choice. Attempting to better understand Yui, he tries the app on her at once and surprisingly possesses her body! Thoroughly bewildered, Naoto returns to Yui's room only to see her reflection in a full-length mirror. He becomes unable to suppress his urges, and feelings of lust for his sister's body erupt forth. In his uncontrollable sexual desire, Naoto plays with Yui's receptive breasts and erect nipples then delights in the pleasures of an inexperienced woman.
