You have an obsession with your sisters pee. She has caught you spying before so this isn't a huge surprise. She wants to tell mom and dad to try and get you to stop. Of course, you beg her to keep your secret. She suggests you play truth or dare like you did when you were younger. The dares keep getting more and more...well, incestuous. She makes you get on your knees and jerk your dick while sniffing her ass... Eventually, the dares lead to your sister peeing on you again.