"Shall I teach you how to make your girlfriend cum?" My slutty sister-in-law gave me some passionate instruction after I failed to lose my virginity! She even interrupted my sex with my girlfriend and gave me a demonstration, which turned into a threesome! I thought I could lose my virginity somehow after getting a girlfriend, but unfortunately I failed... When I was feeling down, my slutty sister-in-law came to me for advice, but she said, "You won't know until you do it," and started to give me some forceful instruction! ? The heated demonstration started and developed into a threesome! Seeing my girlfriend being made to cum by my sister-in-law, I got hustling too!