Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/
works/4733183.
  Rating:
      Explicit
  Archive Warning:
      Underage
  Category:
      F/M
  Fandom:
      Free!
  Relationship:
      Matsuoka_Gou/Matsuoka_Rin
  Character:
      Matsuoka_Gou, Matsuoka_Rin
  Additional Tags:
      Sibling_Incest, Incest, Creampie, Oral_Sex, Vaginal_Fingering, Vaginal
      Sex, Hand_Jobs, First_Time
  Stats:
      Published: 2015-09-05 Chapters: 2/2 Words: 4808
****** Lawless ******
by Ast
Summary
     Gou and Rin and every step they take across the line of appropriate
     sibling relationships.
***** Chapter 1 *****
Rin and Gou are a line of rules broken one by one.
The first one is: you do not get wet by looking at your brother the way you get
by looking at other boys, but that is a simple one to deny - even if someone
were somehow to know, how are they to know that it wasn't Makoto-senpai or
Sousuke-kun? So the first one is this: when Gou lets her eyes linger on the
places where her brother's body bulges and bursts, it makes her slick and ready
for something she knows she'll never have.
 
The second one is: you do not kiss you sister where you would kiss your
girlfriend, but it's been years and years since Rin and Gou were anything like
siblings are supposed to be. They haven't lived together since grade school,
they parted before puberty and came together with bodies grown and ready to
procreate. The person Rin sees every weekend now is an early, budding woman,
and he can tell - oh, he can tell - that Gou looks at him like a man. So if he
holds her just exactly too tight for exactly too long when she hugs him, well,
then that is the consequence of adulthood, and nothing more. It's normal for a
guy to revel in the feeling of a girl's breasts against him; and it's normal
for a guy to kiss a girl who is willing, isn't it?
But he's pretty sure girls aren't supposed to pull their brothers even closer
and press her crotch against his thigh.
 
This is the third one: brothers and sisters do not touch beneath the clothes.
They do not push away shirts and blouses to rest their hands against stomachs
and chests, they do not stroke the fabric of a bra, they do not let their
fingers stroke and revel in swelling muscles. They are balancing on the cusp of
a steep and slippery slope as they lie on Gou's bed, so narrow that Rin always
feels the edge of the mattress and the empty space beneath it.
 
Number four: you do not touch the genitals of your blood-related kin. It
trembles between them as Gou stares into his eyes, body frozen in the motion
that pressed her leg against the undeniable stiffness between his. This is the
point of decision, this is where something must be ended or something awful
must be done, because everything before could be denied and excused and
forgotten, but not this. Rin's fingers clench around Gou's shoulders, and Gou
is breathing heavily, motionless against him. The moment draws out, becomes fat
and heavy around them until Rin uses the grip against his sister to brace
himself, to climb out of her bed without falling on his ass. His action spurrs
Gou into reacting: she grips his arms to hold him in place, and presses her
thigh to his hard-on with purpose.
Rin doesn't know what to read from her face when she looks at her in shock, as
he tries to mask the burst of delight and relief and guilt that is running down
his spine, and Gou will never tell him what it was that made her do what she
did. In this moment of fate, she closes her eyes to him and to everything as
she reaches down to blindly cup her hand around the shame between them. Rin
closes his eyes to that too, as he opens his mouth and pants.
 
Number four is important: you DO NOT touch the genitals of your blood-related
kin. And as this has moved from late night cuddles into afternoon kisses into
secret, before-dinner stroking in his room, it takes weeks and months until it
reaches the point where Rin's hand has pushed the fabric of Gou's underwear
aside so that he can explore her secret places. It is warm and soft and wet,
and she whispers where she wants his fingers, shifts to change the pressure and
the angle, breathes moistly against his collarbone while her fingers are warm
and firm around his shaft. If he was any other guy, Rin could've had this, had
all of her; it would be allowed to touch like this, to touch inside of the hole
his fingers have rubbed against sometimes, to find more wet and a particular
vocality to his sister's sighs. What'd the damage be, anyway?
The moment he pushes inside, he thinks he should've asked for permission. His
fingers slide in so easy, and he only stops when his hand is pressed flat
against her, and she's stilled against him. She's not protesting, and Rin
relaxes, and lets himself enjoy the feeling of being completely surrounded by
her body, of the delicious warmth that molds and folds itself against him. Gou
starts jerking him off again, and he carefully starts making like he was
fucking her, pulling his fingers out and pressing them back in. He thinks he's
finally getting some kind of idea about why sex is so awesome, and then he
realizes that if he was any other guy, that couldn've been his cock instead of
his fingers, and that is when he finally understands how truly fucked he is.
 
What follows is number five: you do not sexually pleasure your brother. Gou
told him that she wanted to look, and after a while of persuasion, Rin let her.
His face is red as he drops his tracksuit bottoms and pulls down his underwear
before he sits back down on her bed with his knees spread. Gou sinks down on
her knees, and uses his thighs to brace against she she leans in closer.
"Wow," she says, and reaches out a finger to run it against the swollen skin,
before she pulls down the skin to expose the head and the crass ridge beneath
it.
"Come on, it's not like you haven't touched it plenty before," Rin gripes,
looking away while his fists are clenched in the covers.
"Yeah, but I never looked," she says in wonder, as the pad of her finger traces
the edge of the head, and the tip dips into the cleft in the front. His cock
twitches, and she clamps her hand around it, holding him steady for a moment
before she strokes down to feel the ridges and the veins against her palm.
"Are you done soon? This is fucking embarassing."
"Oniichan, it's beautiful."
"It's perverse, that's what it is."
"Please, just a little longer," she asks, and leans in to kiss it.
Rin shifts violently at that, his legs moving as if he's trying to stand up,
and his hands are at her shoulders.
"What are you doing?!" he he whispers harshly, staring at her as if this was
all that more scandalous than all the other things they've already been doing.
"I heard some classmates talking. That guys would like it if you - if you lick
it."
Rin is blushing again, but his fingers remain firm at her shoulders, "yeah, but
we, you and I, we shouldn't be doing that stuff."
"I let you put your fingers inside," she says bluntly.
"Did you not want me to?" he asks, shamefaced.
Gou shakes her head. "I liked it. Would you like it if I licked you?"
Rin doesn't meet her eyes as he nods, and Gou braces herself again, holds him
steady, and leans in to press her mouth to the shaft. She pulls back, and
presses her tongue to the thin skin, two times, three, five, ten. Rin's
breathing is heavy, and when she looks up, she finds that he is staring down at
her.
She doesn't ask if he likes it, but leans in anew to taste the head, where the
thin membrane strung tight and and pink with desire. Rin moans lowly, and it
ends in tortured exhalation as Gou lets the tip of her tongue run up the slit
and delights in sensing the geography of his body with her own.
"Hey," says Rin, after a while, "you know, they say it's even better if you
take it all in your mouth."
Gou doesn't answer, doesn't even look up, as she licks her lips and fits the
entire head inside. Rin starts panting audibly, and it takes only seconds
before his cock jerks and her mouth fills with warm, salty liquid.
"Shit," Rin swears, and then repeats it. "Shit. Shit. Gou, I'm sorry, fuck."
Gou wants to tell him otherwise, wants to stop him from blaming himself for
whatever, but before she can do that, she has to empty her mouth. She pulls
back carefully, and finds that she can't keep her eyes from his cock as it
slips off her tongue and hangs in the air, wet with spit and with white semen.
She swallows and wipes her mouth, and leans her head against his knee.
"It's okay," she says and tries to smile, but Rin looks heartbroken.
"It's not okay. It's not right that we do this stuff, and I shouldn't be - not
inside you - "
"Nothing's going to happen. The only place it'll end up is in my stomach - oh,
not like that. You know what I mean. It's like drinking milk."
"That's the most unromantic way I've ever heard someone talk about something
like that," Rin complains, "and anyway, it's the principle."
In liue of arguing with him, Gou presses a kiss to his knee. "I love you,
oniichan."
He slips off the bed and down to her level, and pulls her close and kisses her,
and kisses her, and kisses her.
 
 
Six: if you're going to fuck your sister, at least wear a rubber. But it's not
like they planned to; it's not like they were ever going to let it to so far,
it's not like the temptation was ever supposed to be there. But they were in
the bath together and they dried off together and went into Gou's room to get
dressed together, but instead they ended up here against the wall. It is cold
against his naked back, but Gou's skin is all warm and everywhere around him,
and the world has diseappeared from all around them as they pull as close
together as they can get, and Rin hardly even notices as Gou pulls him away
from the wall and down on her bed instead.
They curl around each other and his hand moves down without any conscious
desicion of his, and slips inside Gou to stroke and curl. She sighs into his
mouth and lifts a leg to give him better access, and Rin -
- Rin's body acts on some ancient instinct as he pulls out his fingers and
instead presses his hips to hers, and feels the wet heat directly against the
thin skin of his cock.
"Fuck," he says and jerks back, and Gou follows, dazed.
"Drat," she whispers, and stares at the sheets.
"That was too close," says Rin, and Gou nods.
"I'm sorry."
"Don't be sorry. It's my fault."
"Not more your fault than it's mine. I really wanted to, and I just forgot.
I've dreamed of it, you know? I've had dreams about what it'd be like if you
were inside of me. Right now, it felt like a dream."
They're sitting side by side on her bed, both naked, Rin still undeniably hard
as he reaches out to take her hand. "For me, too. I've also... dreamed," he
says quietly.
Gou's fingers tighten around his. "Would it really be so bad if we tried just a
little? I know that we'll never be able to be together, so I thought that I
wanted to know as much as possible, while I still have the chance. I know it's
bad, but I want to be as close to you as possible. I just want to know what
it's like."
"Do you have anything?" he whispers.
"I don't, but if it's just for a bit, it should be okay, right? I just want to
know what you feel like inside of me. Just for a few seconds. You don't have to
fuck or anything."
Rin kisses her, and continues kissing her as they fall back on the bed and he
climbs on top of her and she spreads her knees, opening up for him.
He waits for the ceiling to fall down and bury them on the bed when he takes
himself in his hand and finds her entrance, and then presses into her and into
her and into her until he's flush against her and his cock is embraced by her,
wet and warm and pliant.
Her arms are clutching his shoulders and her eyes are squeezed shut, and
inside, she tightens for a moment of bliss. "Oh, oniichan," she whispers, and
that's all it takes for Rin to come.
"Fuck," he sobs against her neck, but Gou's arms only tighten around him.
"I love you."
When he sits back and pulls out of her, he knows that he should be panicked and
shamed at the sight of his sperm slowly oozing out of his sister. But for all
that he tries to tell himself that that is what he feels, he cannot deny that
there is also a firm, steady spike of arousal shooting up through his belly.
 
 
Ten days later, Rin breaks down crying in sheer, utter relief as he opens a
text that simply states, 'I'm on my period'
A week and a half after that, he's once again visiting home for the weekend,
and he's sitting at the kitchen table watching mom making dinner as Gou sits
down next to him and presses something into his hand.
He looks down to find a single wrapped condom, and then he looks up at his
sister in scandal, but Gou doesn't even have the decency to blush as she meets
his eyes.
"Mom, how long until dinner?" she asks, and their mother answers without even
turning around.
"Oh, it'll be thirty minutes at least."
"Okay. Oniichan, come help me with English."
The moment the door closes, Gou reaches up beneath the skirt of her uniform and
pulls down her panties, daintily stepping out of them and kicking them under
her bed.
It doesn't last very long this time either, but considerably longer compared to
that wrecked first time, helped along by the extra layer keeping them apart and
numbing the sensations just a fraction. The condom is a disgusting mess after,
wet outside from Gou's sex and limp and sticky inside from Rin's come, and they
both stare helplessly at it as Rin holds it at an arm's length. In the end, Gou
procures a kleenex, and it is wrapped and wrapped again, and then dropped into
the waste basket under her desk.
Gou leans against the door and Rin lets her skirt fall over his head as he
licks her until she comes. They've barely wiped themselves off before their
mother calls them down.
When they can hear their mother's soft snoring through the wall she shares with
Gou, they go into Rin's room and fuck there, too.
***** Chapter 2 *****
Gou has never smoked, has never tasted alcohol, but she thinks that she knows
what addiction is like, because one day, she wakes up and realises that she
lives for her brother, and that the thought of never having again him is
unbearable. He's at home every weekend when there isn't some kind of
competitiong or swim meet or extra practice scheduled, and they take any chance
to be alone together and kisses are no longer enough. Gou longs to feel her
brother inside her, but even when he is, it isn't enough. She can pretend that
the hateful layer of rubber between them doesn't exist, but she remembers - oh,
she remembers - that first time, and how there was /stuff/ coming out of her
afterwards, so much that she had to sneak her panties out of the house and
throw them away on her way to school lest her mother find out about it.
It should have been revolting. It smelled weird and body fluids were supposed
to be icky, and this was the direct cause of the sickening, desperate worry
about what would happen, what she would do, if her period didn't come. But what
she had discovered in her panties had been the proof of Rin's love of her;
proof that a part of his body remained with her, even as he had left for
Samezuka and the house was once again so empty.
It is dangerous and unhygienic and normally it would be so disgusting, but Gou
wants it. She pretends that Rin is with her at night, pretends that it is his
fingers that are pressing into her even as her arm is bent at an awkward angle.
She pretends until she forgets, until the sensations drown out the reality and
what she feels isn't his fingers, but his cock, and when he moans and stills on
top of her, she imagines that he is letting it all go and giving it all to her.
She pretends a little when he really is there, too. The condoms are hidden in
Rin's room where their mother seldom goes, the one furthest away from her
bedroom, the one where she is least likely to hear a wayward whimper or a
bedframe knocking against the wall. They try to keep it to the times when she's
out of the house. They lock the front door and pull the curtains to whatever
room they're in, and then they're free to do whatever they want.
Gou loves it when Rin uses his mouth on her. It's delicious when he sucks her
breasts, but half the fun of it is to watch his lips engulfing her nipple,
hiding teeth and tongue that are wetly playing her. She loves to feel the firm
curves of his muscles beneath her fingers and benath her mouth; she could spend
the rest of her life sliding her sex against his thigh. She loves feeling him
grow hard in her hand, loves his fingers between her legs, loves feeling him
come in her mouth and most of all she loves feeling him inside of her.
It's a sunny Saturday afternoon that sees them break their self-imposed rule
for the first time. She's on her knees on his bed and Rin is draped over her
back, one thigh pressing rhythmically between her legs as she gasps and
whimpers.
"Oniichan," she complains, and Rin suck's on her neck. "Don't tease, put it
inside!"
"Okay," he murmurs and climbs off her. Gou does not move, already trembling on
the edge of orgasm. Her face is buried in his pillow, and it feels like
eternity as she listens to Rin's naked feet against the floor, the rustle of
clothing being shoved out of the way, and then a soft curse.
"We're out."
When she sits up and turns around, he's holding the empty box between two
fingers, with a look of near disbelief.
Gou very nearly swears, too.
"Shit," says Rin, and dumps down on the bed.
"I'll get more," she says, and can't keep her eyes away from where Rin's cock
is still standing tall between his thighs.
"Yeah, sure. Hey, it's not like there aren't other ways to do it."
"It's been two weeks," says Gou mournfully. "I've been waiting for so long."
Rin smiles fondly. "It can't be helped. I guess we'll just have to do it twice
next time."
Gou falls back and closes her eyes, feeling the arousal pounding between her
legs. Rin is good at doing it other ways, too, but there's something special
about fucking, something that does it for her in ways nothing else can.
"What if you just don't come inside?"
"It's not safe. Not safe enough. The nurse told us, it could still be - you
could still be -"
"I just finished my period, there's nothing there to pick it up even if."
Rin says nothing for five seconds, but then she hears him move and feels the
mattress dip around her.
Gou never had the chance to notice that it's different when you do it withouth
a condom, in more ways than the obvious. There's a different friction to it, a
different slide; and just the knowledge that this is Rin's skin, Rin's body
finally inside her, is nearly enough to make her come.
When she finally opens her eyes again, it is to make the dim discovery that the
framed picture hanging above his bed is rocking in time with her moans.
It kind of impresses her, really, when Rin rears back the second before it
splatters onto her stomach. He stares dumbly at it and reaches out a hand as if
to wipe it away before she stops him.
 
"I looked it up."
"What?" he says, fiddling with her hairtie as they listen to their mother put
on her shoes.
"Safe periods."
"Safe for what?"
"Sex," says Gou in her 'stop being such an ignorant boy'-voice. "There are
times of the month when it's almost impossible for a girl to get pregnant. They
even have calculators, on the internet."
Below, the front door closes behind their mother. Gou straddles his lap.
"'Almost' isn't 'impossible'," Rin argues, and Gou sighs and takes his hand,
leading it along her left thigh until it disappears beneath her skirt, until
his fingertips make contact with coarse hair and then are pushed down into a
soft and wet and needy heat. Gou's cheeks colour and her eyes are hooded as she
guides his fingers to the places where he knows she likes it best.
"Oniichan, I really liked it that first time. I loved the feeling of knowing
that you came inside me. I want that again."
Two of Rin's fingers find their way into her by their own accord.
"Wouldn't it be grand? To just let it all go, without having to remember to
pull out. To come inside. To be inside afterwards. Oniichan, please."
Her hand lets his go, and he doesn't protest whens she undoes his fly. He
slides back on the bed, helps her slide his pants down, and doesn't move an
inch as she moves astride of him again, takes him in her soft hand, and slides
down until she is sitting flush on him, his cock sheathed entirely inside her.
She's gasping softly as she rides him, and he lets her decide on the speed, the
rhythm, the depth, focusing instead on unbuttoning her uniform blouse. It hangs
prettily around her, and then he reaches behind her to unclasp her bra. The
cups still cover her, but they hang looser now, following the motions of her
now freed breasts.
Gou says nothing to this, only groans as he reaches up to squeeze a still-
hidden nipple. The feeling of her cotton stockins agains his bare thighs is
incredibly sexy, as is the view of her bra bouncing in rhytm with her.
"Is it really okay if I come inside you?"
"Yes, oh yes," she breaks off in a particularly sharp groan.
"I'm not going to hold back," he warns, as he takes a hold of her hips so that
he has an easier time meeting her halfway.
"Good," Gou pants, and smiles, and starts fucking him faster than before,
louder than before. She's whimpering every time he goes in now, and Rin drowns
on those sounds, and the rustle of her skirt, the squeaking of the springs
beneath them, the tiny squelches from where their bodies are connected, and
forgets to ask if it is okay as he starts pulling her down faster and harder.
He still can't quite believe that he gets to have Gou like this; it's
impossible and it's illegal and it's insane, but Rin has never wanted a girl
like he wants Gou, and Gou -
Gou is making words now, oniichan, oniichan, give it to me, please,
and Rin screams as he comes, jerking her down one final time to hold her in
place as he empties himself deep inside her.
His hands are shaking as he comes down and lets go of her hips, falling limply
back against the pillow. He opens his eyes to look at Gou, and he finds that
she's looking at him with a shocked expression. She's completely still above
him, but he can feel telltale contractions around his sensitive cock. He lifts
her skirt without a word, and uses his other hand stroke her swollen clit.
Gou's thighs relax and she rests her weight on him, dropping her head to pant
as he lightly runs his thumb up and down over it.
"I could feel it," she says breathlessly. "Oniichan, I felt you squirting
inside me."
"Seriously?" he says in amazement.
Gou pants louder and starts rocking lightly.
"Yes. It was so hot - " and then she comes, keening outside and squeezing him
inside.
Afterwards, they rest in the same position. Rin runs his hands up and down
Gou's back as Gou's breathing goes back to normal against his neck. The room is
so quiet now, the house all empty, and he stares at the ceiling as he caresses
Gou's thighs.
"That was really good."
"I could tell," Gou murmurs dryly, and lifts her hips slightly to meet him as
his hands cup her buttocks. Rin can feel her nipples pressed against him
through the fabric of his t-shirt, and unbelievably, he feels himself wanting
another round already. He brings one hand up to cup the back of her head, while
the thumb of the other worms its way between their bodies until he can press it
against her left nipple. She sighs in approval.
"What time is it?" she asks.
Rin looks at his wristwatch. "Quarter past four."
"She won't be back until six," says Gou as she sits back, and carefully climbs
off him to start shedding her clothes. Once she's naked, she turns back to him
and giggles.
"What?"
"You look silly. Fully dressed, just your pants pulled down, and with your cock
standing out."
"Oh, fuck you," Rin growls as he sits up to kick the pants off and pull the t-
shirt over his head.
"I just did!" Gou laughs, and comes back onto the bed, naked skin hot against
his. Her mouth is as warm and soft as ever, and he pulls her close as they
kiss, deeply, and Gou already is making motions to start again.
It's slower, the second time. Gou lies on her side, and obediently lifts her
leg to let him in between. She's still swollen and glistening with arousal, but
Rin still spots it, that smear of white fluid that he left with her, and that's
starting to come out. She's still sensitive from before and doesn't want him to
touch her clit, but she sighs contentedly when he slips into her again. Rin
makes his thrusts as deep as he gets, and takes it slow, grinding against her
every time and listenting to her sighs and soft moans.
She is beautiful beneath him, spread out on his on her bed. She could be
sleeping; her head is resting on her pillow, her eyes are closed and her body
is fully relaxed as she receives him, rocking lightly with every thrust. Her
skin is smooth and soft, her hair beautiful in the afternoon sunlight, and she
is tight and warm around him, wet from their shared juices as she embraces him
in ways he would never have dared to dream about before.
"I love you."
It is entirely redundant. Of all the things that the two of them have ever said
or not said to each other, this was the least secret thing of all. For all that
Rin might have pulled away from his friends and his classmates and, yes, his
mother, he never pulled away from Gou. For all the things they have been doing
to each other these last months, it was obvious they wouldn't be doing them if
they didn't love each other. He knows that Gou knows it, but he suddenly needs
to hear the words.
"I love you, Gou," he repeats into the silence of her bedroom, while he's
fucking her bareback for the second time in thirty minutes. It should be
absurd, he thinks. Instead, it feels like everything finally makes sense. In
that instant, he can finally see that this is something he cannot end, that he
can't run away from this girl and that she doesn't want him to. He doesn't know
how they'll work it out, but just then, at that moment, he realises that
they'll make it work somehow, and that this is where his future lies. All the
worries, all the shame, all the guilt evaporates as Gou opens her eyes, and
turns her head to smile as she gives him everything back in return.
Please drop_by_the_archive_and_comment to let the author know if you enjoyed
their work!