Don't push your luck, get the keys and get out of the house.

You need her help but right now you have no way to make her do anything if things go south. You decide to quit while you're ahead and pull your cock out of your poor little sister's mouth.

"That's good, you little slut. I'm going to make you tongue bathe my balls on the regular from now on if you disrespect me like that again. Do you understand me?"
"COUFF- COUFF-"

Vanessa looks up at you fearfully. Her tear stained face elicits a moment of sympathy from you but you're too far up your own ass to truly appreciate what you've just done to your own little sister.

"Smart girl. I told you what I'd do if you opened your mouth without permission again. I'll be back later tomorrow to talk to you, I better not hear about any of this getting back to mom and dad, or I'll stop time for a month and break you permanently. I got shit to do, so I need dad's keys. Now get the fuck out of here before I change my mind."

You push your sister roughly to the ground, and she crawls away from you, her taut little body makes your cock twitch again, but there's a time and place for everything. You need to get out of this house before your sister figures out that something is wrong.

You go into your father's study and get the spare keys from the drawer and head out to the garage.