Sometimes the best moments aren't planned. Just spent the afternoon with my eldest sister helping her study for finals - started with flashcards, ended with her bent over that textbook with my cock buried deep in her tight ass. The way she moaned 'don't stop, I'm so close' while trying to solve equations was fucking priceless. Nothing beats watching a smart girl lose her composure when she's getting properly fucked. Who else finds intelligence the biggest turn-on?