Hot Summer Job/Leave her alone for now
You are still stunned by all that just happened. You look down at your slimy flacid cock and the trails of your cum running down your thighs where it had been dripping out of Bree's hole onto your balls. It suddenly starts to hit you, you just fucked your sister. Good lord, if your mom ever finds out about this, you're dead. You look down at the glob of semen that dropped out of Bree's vagina before she ran off. It is on the entry door mat. That thing is graody enough that you are sure no one will ever notice once it dries, but what about what may have leaked out while she was making her dash up the stairs?
Well, first thing's first. You gotta get yourself cleaned up. You run off to the downstairs bathroom and begin tearing off sections of toilet paper to wipe the rivers of semen off of your thighs and balls. Every time you tear off another square, there seems to be more. The stuff got all over your legs, having run from your crotch to your ankles and down onto your heels, you probably tracked some of the stuff across the floor on your way here. You can hardly believe all of this came from you, and every last drop of it was inside your little sister's “forbidden garden” before it ran back out to get on you. Your dick begins to start getting hard again as you take a section of toilet paper and wipe down the shaft while thinking about how the little elementary schooler is upstairs right now filled with your white baby-goo and is doing something very similar to what you are doing right now. It is almost laughable how slimy the toilet paper comes away before you chuck it into the bowl.
You hardly feel that you are even half way through the task when you hear the upstairs bathroom door opening again, guess she must have somehow been less slimy than you, at least on the outside of her body. Well, her legs were up and wrapped around your hips the whole time, guess her legs managed to stay clean. You quickly run the next square of toilet paper over your legs. You are not completely clean, but it is probably close enough to hold you until you can get into the shower.