You come home on your birthday and are surprised to see your wife's sister waiting for you in lingerie! She explains to you that your wife told her how you've always wanted to fuck her. So for your birthday, your wife and her sister have gone in on a present together - a one-time pass to fuck your sister-in-law! She starts by sucking your cock, then pumps you between her tits before letting you fuck her pussy. Of course, she can't resist throwing in a few comments about how she's a better lay than your wife, and implying that this might not be the last time you get to fuck your sister-in-law!