In Her Mouth!

You take a few quick, final strokes into Rachel's tight ass and feel yourself ready to cum. You climb off her and roll her over. You have a sinister grin as you are about to make your little sister taste her own ass. As she flops onto her back, you crawl up her body, sitting on her chest and start stroking yourself over her face.

"Open your mouth, NOW!"
You grab the top of her head and jab your cock at her closed lips. She doesn't open and you smear you dick all over her face. Growing impatient, you smack her in the face with your dick hard, leaving a red, dick-shaped mark on her cheek.
"OPEN THE FUCK UP!"
She whimpers but opens her mouth and you plunge in. Her face scrunches up in disgust, obviously tasting her ass on your cock. You fuck her face for a few seconds and start to squirt into her mouth. Rope after rope of your cum paints the back of her throat and her mouth begins to fill with cum. You quickly pinch her nose shut, forcing her to swallow in order to breathe. You keep spurting, dumping a huge load into her mouth as she struggles to swallow it all. Once you are done firing, you release her and back away, letting the last few drops of cum fall off the head of your dick onto her face.

You look down at your hot little sister. She has a long dribble of cum leaking out the side of her mouth all the way down her neck. She spits and sputters while swallowing your cum and glares angrily back up at you.
"You fucking dick."
You laugh and slide down her body a bit, but don't get off her yet.
"Actually, YOU fucked MY dick, sis. With your ass."
You reach down and play with her tits while she regains herself. She reaches up and wipes the cum off her face and smears it on your thigh.
"Fuck, you got your cum all over my fucking pillow."
You realize the whole bed is a wet mess of fluids.
"Oh well", you say to her, "just do some laundry, it'll come clean."

You finally get off Rachel and stumble out of her room. She gets up slowly after you and begins stripping her sheets off the bed.
"Jerk."
That's the last thing you hear before heading to the living room and plopping down on the couch. Claire comes in behind you.
"Oh, David, good, you are up. I have to head to work but I would like you to help your sister's clean up the house while I'm gone."
You lean back on the couch to look at her.
"No problem, Claire, Rachel's already started laundry."
Claire grabs her keys and heads for the front door.
"Good! I'll be back for dinner."
And with that, Claire leaves for work. Now, you're sitting on the couch with the whole rest of the day ahead of you, what's your next move?