My step-sister, who is living in the house, gets aroused after witnessing my wife's intense orgasm...

Nao, a younger sister who lived a nerd life in the countryside, moved to Tokyo from her hometown as soon as she graduated from university. I don't have any work or room, so I decided to stay at my sister and her husband until I was found. However, the nightly sex between her sister and her sister is insane, and her younger sister Nao is shocked. She peers at her violent thrusts that seemed to break, moans like screams, and leaning her body back and reaching climax many times, making her crotch wet. And he is unable to stop his overflowing desires and takes bold action...