My biggest fantasy role play is that my gfs sister has been round ours before heading out with her sister and some friends , she is staying at ours so has an overnight bag with her and as im putting it in the spare room i notice its open and see her panties in there , i can't resist so i take them out the bag and put them on . As i lay on the bed rubbing my cock through them panties i don't hear the door , its my gfs sister , she had also left her purse in the bag and let herself in the house and is now stood staring at me rubbing myself wearing nothing but her little panties