Your older sister Anna is planning a fancy dress party. Naturally you are not invited but your best friend managed to snag an invite so you crash with him. Anna likes your friend and spends the evening chatting him up and slutty dancing in front of you to wind you up. As a prank, you swap costumes with him and put his mask on. She comes back in the room and asks if he (now you) wants to go somewhere quite. The plan is to record her saying dumb stuff and flirting and then blackmail her for the rest of the year. But she is just so fucking sexy, you cant help yourself you get hard. Before you can stop the prank, she has your cock in her mouth and you cant think about anything other than blowing your load. When you tell her your a virgin, she says its ok and that she will teach you what to do. You are surprised she did not recognise your voice. You finish after a couple of strokes and are ready to run away and never talk about this again, but she tells you to take the mask off and eat her pussy, she lies back and closes her eyes, no idea her own brother has her pussy juices running down his chin. She looks down, and FREAKS out. Before she storms out, you grab her arm, pull her hips and sit her down on your cock. She fights it, but you know she loves it. You spend the next ten minutes sibling fucking in a party full of all your friends.