Cosplay Turned My Sweet Stepsis Into a Total Cock Fiend!

My stepsister wanted to go to a comic convention dressed like a slut! I knew her outfit was a cosplay, and she looked hot, but our parents put me in charge while they were away, so I was not going to let her go out looking like that. Everyone would be picturing her naked, just like I was doing! All it took for me to change my mind was for her to suck my cock dry while wearing her slutty costume.