Masturbate and cum in her mouth
From Create Your Own Story
-It takes you around 5 minutes of masturbating to finally reach your limit. You get up the more you can in the car and let over 250 mil of cum fall into your sister's mouth. It quickly overflows wile she tries to swallow the mating sauce. Over 150 mil of white stuff is sliding in her throat. Garggulp...aaarg koff koff, thats like... koff 10 times more cum than my boyfriend... koff. Your dick is 3 times longer than his! You smile at her while she tries to stop the cum drips from falling on the floor. You help her to clean the mess and see that all her makeup is messed up.
You decide to Just drop her off and get to the expo.