On a day off, an older sister spends her time without underwear or a bra. Upon closer inspection, her vagina is intermittently visible… The sight of her vagina peeking through the gap makes her virgin brother's erection unstoppable. The faint, lewd scent of her vaginal aroma… Is this coincidence? Or was it inevitable!? Her exposed erotic vagina seduces her brother, who mistakenly thinks he's being tempted and can't help but immediately insert his penis! Her defenseless, underwear-less sister's vagina swallows her virgin brother's penis, and she comes undone with a virgin piston thrust. How many times can he ejaculate inside before their parents come home!?
