My married sister came back to her parents' house after a fight with her husband! We used to share a room, so we decided to sleep in the same room like we used to! This is the perfect opportunity! I gave my sister, who I secretly had feelings for, an aphrodisiac... and it worked too well! Her whole body became an erogenous zone and she became super horny! She arched her back and came over and over again, and just before I came, she forced me to cum inside her with a crab-style position! Extremely radical incest!