I might not be the strongest or the smartest, but I know a good opportunity when I see one. My stepsister Lily is curvy in all the right places - big natural tits & a fat, juicy ass. When I tell her I could use some advice in the bedroom area she basically laughs me off. But then she realizes nobody is going to help her with her math homework - then comes the pinky swear proposal. She helps me get more experience & I'll tutor her in math. Opportunity, see? Well that wasn't the only thing that rose when she pulled out her big, beautiful tits. She jerked my cock off & it started getting her horny! She climbed on top and slid her wet pussy on my dick, I squeezed her big boobs as she bounced up & down. I fucked my stepsister hard from behind, making her big ass ripple and her pussy cum too. I couldn't help it and busted right inside her! She didn't seem pleased, but I'm going to tutor her super hard this week.