Motherfucker, I remember writing this.  I know it's mine because of that "allow me to spare you the indecision" line, which I blatantly stole word for word from a FF7 fanfiction called The Fifth Act, chapter 37, and I fucking love that line.  Also, I remember writing that bit where Maud blinks one eye at a time and Anon doesn't know if she's hungry or if she loves him.  And that line in the breakfast scene "Nobody won this morning." was stolen from a picture I saw of a crying child and a cat with a sucker stuck onto its fur, which had the comment "Nobody won today" on it.  And finally, it just plain has my writing style.  See?!  I'm not just taking random greentexts from the archive and claiming them as my own!
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>Maud calmly explains to you why sexual activity isn't something you need to keep secret from her. She logically goes through how she already knows about it and thus any hope of secrecy is gone.

>Maud tries to convince you to start a relationship with her
>"Neither one of us are in a relationship with another person, and both of us have sexual desires. You are a man, and I am a woman. There's no reason for the two of us to suffer from being alone."
>You try to explain why you can't just do that with family, but Maud interrupts you by grabbing the hem of her frock and flashing you, revealing that she isn't wearing underwear

>"You masturbate quite frequently, Anonymous."
>You nearly spit out your coffee at the way Maud casually starts talking about masturbation at the breakfast table.
"Wh-what!? H-Have you been listening at my door?"
>Maud shakes her head and sits down next to you.
>"No, but I don't need to."
>Maud grabs a slice of toast and begins to spread butter onto it, starting on the outside by the crust and meticulously working her way in towards the crispy brown center.
>"Your bedroom and my bedroom share a wall, and so do our beds."
>Maud takes a bite out of her toast and stares off into nothing.
>"I usually stop what I'm doing and masturbate along with you. It makes my orgasms feel much better than when I do not get to listen to your moaning."
>You stare straight ahead, just like your sister, but for very different reasons.
>You wonder if it's possible to die of embarrassment.
>You wonder if the world is merciful enough actually LET you die of embarrassment.
>Maud grabs the old-fashioned percolator and pours herself a mug of coffee.
>"We should start having sex."
>This time, you DO spit out your coffee.
"What the FUCK, Maud?!" you shout, doing your best to recover from inhaling your morning beverage
>Maud turns her head and looks you in the eyes.
>"Both of us have desires, Anonymous, and neither one of us has the responsibilities or obligations that come with a romantic or sexual relationship with another person. Having sex with each other would lower stress levels in both of us and would make us feel more pleasure than if we continued to masturbate in separate rooms."
>Why is this your sister.
"Maud... we can't just have sex with each other."
>Maud, having gotten bored of looking at you, turns her attention back to her breakfast.
>She takes a bite out of her toast in exactly the same place she always does every single morning (top-left corner with the intent on taking bites in a counter-clockwise direction, working inward)

>"If you are concerned about the frequency of our copulation being less than the frequency of your masturbation sessions, then you do not need to worry: My vagina become very wet when I think about having sex with you, and I would be more than willing to couple with you any time I am not busy with work on the farm."
>Whoo-boy.
>You tug at your collar and push your half-empty mug of coffee (the other half having been sprayed across the table) away from you.
>You don't need a hot beverage any more.
>If anything, you need something cooler.
>Like a cold shower.
>Maud looks at you again, and this time you can pick up the faintest pink blush on her cheeks.
>"You feel hesitant. Allow me to spare you the indecision."
>Your sister pushes her chair away and stands up in front of you.
>Maud's nimble fingers play with the buckle on her belt, and you're hit with the realization of what she plans on doing.
"M-Maud! Maud, we're siblings!"
>Maud replies with a bored-sounding "Irrelevant." and finishes undoing her belt.
>Immediately after, she grabs the hem of her frock and lifts it up.
>Luckily for Maud, your face is at crotch level.
>And guess what you see?
>A crotch.
>Your sister isn't wearing any underwear, and you can see just how wet, red, and swollen her vulva is.
>"As you can see, I have been thinking about having sex with you since I sat down for breakfast a few minutes ago."
>...
>M-Maybe just this one time would be okay.

>"Ahh!"
>"Oh!
>"F-Fuck!"
>Limestone growls in irritation, opening up her bloodshot eyes and staring deep into the dark corners of her bedroom.
>She yanks the pillow out from under her head and roughly wraps it over her ears.
"Can't a girl get some SLEEP around here?!"
>She aims a blind kick behind her and is rewarded with a pain in her heel and a loud THUNK from the wall behind her; the wall she shares with Maud.
"It's 2 AM, you pricks!"
>"S-Sorry, Limey!"
>Limestone huffs and closes her eyes, trying to shove the sounds of her perverted siblings having sex into the back corners of her mind so that she can FINALLY FUCKING sleep.
"I can't believe those two, Marble."
>She shuffles around and tries to find a position that will keep the pillow pressed tightly against her ears without her having to actively hold it in place.
"It's bad enough that they're actually having sex with each other. Can't they at least have the decency to keep it quiet?"
>Limestone doesn't hear a response from her sister (the GOOD one), and busies herself muttering disparaging things about Maud and Anon as she tries to fall asleep.
"At least... at least neither of us are degenerate perverts like THOSE TWO are, right Marble?"
>A whimper, barely audible through the pillow wrapped around her head, makes her eyes snap open.
>Hours of laying awake in a dark room have given her eyes plenty of time to adjust to the dark, and so it isn't hard to spot her sister.
>Marble, face flushed with blood, is biting down hard on the hem of her blanket and her arms are jammed under the covers.
>With all that movement wriggling around at about crotch-level, it doesn't take a genius to figure out what Marble is doing, and why.
>Limestone groans and flips the pillow around so that it's now covering her face (and most importantly, her eyes)
"For fuck's sake, you guys. Really?"

>Breakfast is an awkward affair.
>You try to focus on your meal, but the toast (with peanut butter on it) seems to crunch too loudly for the tense atmosphere to allow, and the flavour of sweet peanut butter on homemade bread seems absent.
>Across the table from you, Limestone shoves a piece of orange into her mouth, not once breaking her angry eye-contact with you.
>Even the way she chews is aggressive and rough, and you get the feeling that she cares more about destroying the orange slice in her mouth more than she cares about properly chewing it so that she can swallow.
>Maud returns to the table with her plate of usual breakfast: toast (soon to be slathered in homemade butter), an egg, and a cup of orange juice.
>She sits down on her chair next to you and, as she has taken to do since you began having sex, scoots over towards you until her hip is pressing against your own.
>Much like your chewing, the sound of old rubber chair-leg nubs scraping against a dry hardwood floor seems to be too loud for a room as thick with tension as your kitchen is.
>It's almost invasive, as if it'll set of an unseen bomb if Maud isn't careful enough moving around furniture.
>When you feel the warmth of Maud's side, you break eye-contact with your grumpy sister and look over at your not-grumpy sister.
>You smile at Maud, and she stares blandly (almost unseeingly) back at you back.
>There's a long pause, and then she blinks one eye, and then the other.
>D'aww.
>That means "I love you".
>...or "I'm hungry".
>...
>Or "I want to have se-" you know what? Maybe you aren't as good at reading Maud as you would like to be after all these years of living with her.
>You decide to bump Maud's side with your elbow for good measure and hear a growl from across the table.
>Chunks of crispy bacon tumble from Limestone's clenched fist as she squeezes the bajeesus out of a couple of strips.

>Her eye (specifically the left one) is twitching dangerously; you recognize the tell-tale signs of Mount Saint Limestone building up for an eruption.
>"Can't you two," she growls out, bearing her pulp-stained teeth at you, "keep it in your pants for FIVE MINUTES?!"
>She balls up her shaking hand into a fist and slams it down onto the table, making all the dishes jump.
>The percolator, in particular, seems in danger of dipping over; it spins around and dances on the rim of its base before settling down a few inches away from where it sat before.
>"All day, every day, I hear you two perverts going at it like a pair of incestuous bunny rabbits! It's bad enough that Ma and Pa don't seem to give any number of shits that you two are doin' it, but now Marble and I have to listen to you FUCKING each other all night long! Can you at LEAST give us respite from your perversions during breakfast?!"
>Limestone slams her fist back down onto the table, and the dishes jump again.
>An orange bounces once and rolls off of the edge of the table, and the percolator-
>"Aah! Ow, fuck!"
>-tips over and spills all the steaming-hot coffee right onto Limestone's lap.
>You glance down at your clean, empty coffee mug and sigh.
>Nobody won this morning.

>In a flash, Maud is out of her chair and moving to intercept Limestone.
>With a bundle of napkins in hand, Maud doesn't hesitate as she reaches down and pulls the front of Limestone's pants away from her crotch.
>You catch a hint of whispy gray pubic hair before Maud jams her hand (the one with the napkins in it) down Limestone's pants.
>Limestone just sits there, stunned; like a pissed-off deer in an oncoming car's headlights.
>It's like she doesn't know how to react or which emotion should take precedent: anger at being touched "down there" by her sister, or relief that severe burns have been averted.
>Maud seems dead to it all as she dabs her sister's bare crotch with the napkins, making sure to soak up any of the rapidly-cooling coffee she comes across.
>The last thing you hear before Limestone flips the breakfast table is Maud:
>"Let's get you out of those pants, Limestone."