you and your older sister are home from college for winter break, just hanging out. she asks you out of nowhere if you ever fucked one of your girlfriends in the ass. "really? never? i mean... i just think it's fun and cool, i think more people should try it." you try not to think too much about how tight your big sister's ass could be, but it's no use. one thing leads to another and she points out your huge boner. she teases you, but assures you that it wouldn't be that bad if you had anal sex with her. after all, it would be way more fucked up to knock up your sister, right? your big sis really wants a cock in her ass, and she doesn't seem to care if that cock is her brother's. in fact, she really plays it up once you take your dick out, "you wanna put your fat dick in your sister's fat ass? haha!" your sis presents her ass for you and starts fingering herself, and you cave and agree that you want to screw her. and what do you know; your horny big sister takes your cock in her ass almost TOO well!