Your step-sister is always nagging and being a bitch to you, so you decide to teach her a lesson! You know her secret fetish, and decide to have some fun with it! You Push her against the wall and start jerking over her stomach. She tries to resist, and pretend she isn't into it but she can't deny her fantasy, you can tell she is into it. As you jerk her belly starts to grow and you finish all over it making it grow more! She demands that you continue to jerk and cum all over her belly and keep it growing, growing until it pops!