Barely

With your back to the door, your hand is flying on your cock, smearing a combination of your sister's pussy juice and your drooling precum. The mental picture in your head moves from Liz back to the milk chocolate of Clarissa again, and you watched as her tits filled out, but she was still wearing your sister's camisole. Clarissa wore it better.

"Don't cum again before our date," you heard Clarissa say in your head, but your hand and hips had a mind of their own. Thrusting, you realized you were bouncing slightly against the door, making it subtly, quietly thump in motion with your hips and then it just stopped, even though your hips were still pistoning your cock in your hand. It was as if something was pushing against it from the outside...

It was Liz. She was leaning against the door. Fuck, was she listening, was she...

Liz moaned. Barely loud enough to be heard. She whispered something you couldn't make out and your cock surged even harder in your hand and you started fucking your fists...both of them, sliding your cum-slicked rod through them like a pocket pussy, the head blooming on the other side as a full inch stood clear of your hands before disappearing back into them. The picture in your head was of your sister on the otherside of the door. Pressing against it. Moaning as you fucked your hands wishing it was her. Fantasizing about her mouth and her pussy.

Your hands tightened, a distant part of your brain wondered if this was as tight as her pussy would be. If pushing into that velvet, soaking, tight box would feel as good as the girls at college...or...

...better...

Your ass started thumping harder against the door, driving your cock in and out of your make shift fuck toy as you imagined your little sister bouncing on your cock in visceral detail like you've never imagined before...

And Liz's voice grew...