Let's check the bathroom.

You see that in her hurry to clean herself of the cum on her your sister dropped her dress on the floor, stopping the door from closing.
You stop time to get a better look. She's in the shower washing her chest, all traces of your cum is already gone but she still touching her tits under the jets of warm water. Not only her tits, her pussy too...
"What a slut! This thing didn't piss her off, it turned her on. Well sis, I have got exactly what you need! " you tell to the frozen world between seconds.

You strip down, leaving your clothes in your room, not sure if the watch is waterproof you go pick some plastic wrapper to put around it. On a last hunch you pick every towel or cover in the bathroom and her dress and go put it in the laundry in the basement.

You enter the shower with her and turn her body around brushing away the strings of water around yourselves.
A check to her pussy, yes it is really wet and none of it is water.

You're pretty sure that with the watch you'll manage to get yourself a girlfriend, if only that the rewind function is basically the ability to load a save point and entry like in a video game. But in the mean time it is already past due for you to try some pussy and your sister's bitchiness just volunteered her as your fuck doll.

You lift her and set her with her legs parted, facing you, floating in the air at just the right hight and angle. This is it! You put the tip of your dick on her pussy and slide in. The slick warm flesh of her pussy is wonderful.
It's not that you're ugly but you were not popular in high-school, Chad bullied you and your sister liked to lie about you to other girls to mess with you. Few wanted to date the weird boy with strange rumors about him, especially if they would lose reputation with the team and cheerleaders.
The only dates you got were with Marcy Thurston, but her strict religious upbringing made her refuse to do anything serious before wedding, even the few hand jobs you got from her she did on days she was passed at her parent, more out of rebellion than love for you.

This is different, this is the real thing! You're fucking your sister's sweet pussy. (you're far from the first to do so.) it's a good thing you came earlier or you would have gone in seconds, but then you had all the time in the world. After stuffing her pussy you decide to take a little break. The part about electronics not working socks but you find an old port mag hidden somewhere (and 357$ of your sister's secret stash that you take, the device was not cheap it should pay for itself and more in the long run.) you simply go read it naked in the front yard.
After 30 minutes (approximately, no time remember.) you go back to the shower for a tit fuck.

It might be better with a girl moving and reacting but you manage to cum on her face quite easily.

You go back to your room, leaving the bathroom door slightly open and your bedroom wide open. She would have to go in front of your room to go to hers.

You put some boxers and the t-shirt you had before and just lay on your bed with your phone in hand like you're reading. (you will turn the camera on the second time restarts.)
Everything in place, you unwrap the watch and press the button.

"What the fuck!" you hear your sister scream from the bathroom.