TMHK-016 - K-cup masked slut turns out to be my plain-looking younger sister.

Mikoto, a plain-looking girl with glasses, accidentally catches a glimpse of her brother's erect penis and becomes obsessed. Unable to control her urges, she decides to wear a mask and assault her brother. Despite the mask, her true identity is obvious to him. She becomes obsessed with his cock, appearing out of nowhere to force herself on him and demand he cum inside her. Even when her brother is completely exhausted, her insatiable lust refuses to fade.