Kareki Tsunetaka is a veteran "Home-Security Officer" of 20 years. One day, his home is encroached upon by the woman his father remarries: Katsuragi Shouko, a former widow with a body too good to be wasted by widowry.
Tsunetaka, through his intuition honed from being a home-security officer, deduces that Shouko plans to take over their household. In order to protect his home, Tsunetaka sets his sights on Shouko's younger daughter, Yuki, searching for blackmail material through various surveillance devices. Through constant surveillance, he lays witness to her small yet beautifully formed breasts, unwary glimpses of her inner thighs, and most importantly: her intimate moment with her girlfriend, all caught on camera.
With this blackmail material, the home-security officer lays waste to her virginity, plugging her impertinent mouth with his rod, and penetrating deep into her previously untouched areas.
The next target... Is the sister, Katsuragi Yuki!