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To Always Be Together

Summary:

It’s been a little over a month since Tanjirou and Nezuko confessed their love for each other, and Nezuko is feeling the peer pressure from her friends and Ume about how far she should let things go. But she and Tanjirou are in love, and she can’t ignore her needs much longer.

Notes:

This is the bonus smut oneshot for my multi-chaptered Kimetsu Academy AU fic, Through the Open Window. I guess you can read it on its own if you just want some smut and don’t care about the context, but the references to the “world” of the story would only make sense if you’ve read the full fic. Either way, I hope you enjoy!

(See the end of the work for more notes.)

Work Text:

I want you.

 

Tanjirou had first said the words to her, breath hot as his mouth was pressed up tight against her ear where he had been licking the ridge and kissing her neck, weeks ago now. Nezuko’s body had reacted then before her mind could process it. Her own breath caught, her core tightened, and a silky heat slid down her body, washing over every inch of her down to her toes with excited anxiety. Her body, betraying her, reacted with a matching want, but the urge to give in remained contested in her head.

Her school friends were a source of unending turmoil with how badly she wanted to fit in at their level of daily concerns in life, even considering her relationship was a secret. They all acted like boys had cooties while simultaneously longing for their own love stories, saying that they wanted romance but wouldn’t dare let a boy get in their pants “so easily.” At the same time, Ume assured her that being constantly intimate with what could only be described as the other half of her soul was normal. More than obviously expected, sex with Tanjirou would be fulfilling in a way words couldn’t express, though Ume tried and tried to get Nezuko to understand—or maybe accept. The dramatic girl was beyond frustrated that Nezuko hadn’t taken that next step, because she couldn’t talk about it with her; she had always been alone in her relationship with Gyutaro, and disturbingly found she desperately needed a girl to connect with on the matter. Nezuko’s friends at school were scandalized by sex. It was a drastic tug of war based in the matters of teenage romance. She was hardly able to make sense of these polarizations of opinion, wondering where she could or should fit in.

Then there was the undeniable fact that she did love when Tanjirou touched her, and he was simply all over her. Every night when they were home alone together, he wrapped his arms around her waist and kissed her passionately when whichever one of them was out finally got home. They held hands and held each other while doing chores around the house, giggling and kissing when they were cooking and cleaning. Later, they’d end up tangled on the couch together, lost in deep, hot, heavy, wet kisses; Tanjirou’s yearning hands made their way under her shirt; in bed at night it would happen again, his wandering having then made it under her pajama bottoms and between her legs. Was it shameful of her to allow it, or the natural recourse of the progression of their romantic love, even if she worried it was too soon? What was too soon? Ume was right that her love with Tanjirou was stronger than anything in any universe, and her heart would never change on that fact—so maybe it only made sense to become fully intimate without any wait. And, even though it was hard for her to admit it to herself, when they were engaged in the sexual activities they already practiced, she wanted it.

But was that wrong? Did it matter? It frustrated her endlessly that she couldn’t reconcile her thoughts and feelings with herself.

Tanjirou, on the other hand, was a mess, though in a completely different way. He was horny—badly—worse than he had ever been. Masturbating in the shower was more common now, under extreme torture with how close he got to Nezuko without being able to fill her (in his fantasies, since he knew very well he needed to use protection). He had even licked and kissed her between her legs once—just for a moment—and now that was Heaven—but he was still unable to fully have her. The thoughts shamed him, because he didn’t want to pressure her. He asked her constantly if she was alright, entirely at the mercy of permissions given or not given. He would absolutely never hurt her, and would care for her at every turn of their developing relationship, whatever she needed—even purely emotionally, as sometimes he couldn’t tell if she needed him as a brother or a romantic partner, or what that even meant for them now. He loved her, well and truly beyond anything his senses could process, and wanted only to be as close to her as he could be; which included, regretfully, to own her in a way that no one else ever would. He felt guilty for that, though Gyutaro assured him that he shouldn’t. In some ways, he may have been just as confused as Nezuko.

Still, he bought a pack of condoms at the convenience store where his friend worked—just in case.

One evening, on no day of special circumstance in particular, he reclined on his bed with his head propped up on pillows as he tried his best to decipher the assigned English literature book. He had already showered and gotten ready for bed, but was still working to catch up on his homework before final exams. He was determined to do his best, as he had promised Nezuko and his great-uncle that he would recover from his suffering grades. He no longer had soccer as an excuse, so it was down to studying or pure slacking off.

Nezuko entered the room like a vision after having gotten ready for bed herself, her long dark hair still slightly damp. Even in a plain pajama set, she could never not look unearthly beautiful to him. She was pretty enough in day-to-day life that he was constantly struck by her, so whenever he got to see pieces of her naked body he practically salivated, worshipping every inch of her that he was allowed. Her breasts were the perfect size, delightful palmfulls, and she was the perfect shape between her legs, the juices he had once gotten to savor tasted and smelled so sweet. In plain terms, he was consumed by his love and lust for her.

“Hi, nii-chan,” she said when she closed the door behind her, somewhat sheepish when she took in the sight of his handsome face and broad shoulders. He wore a soft blue t-shirt that was often one of his sleepwear choices, and she loved his athletic arms, the ones that held her so tenderly, and made her feel entirely safe, as though nothing in the world could ever hurt her again—especially in the early hours of the mornings when she often woke up crying from her nightmares.

“Hi, Nezuko,” Tanjirou said with an easy smile, forgetting the book entirely, probably even the name of it and the entire page he had just read. “You look pretty,” he told her.

The lightest bit of pink tinged the tips of her cheekbones as she looked down and played with the folded edge of the comforter.

“I’m just in my pajamas,” she said, thinking she also wore no makeup, and her hair wasn’t styled, just washed and clinging to her neck and down her back in heavy straight lines.

“That doesn’t change anything about you being the prettiest girl I’ve ever seen,” Tanjirou said.

Nezuko pulled the covers back and carefully slid into the bed on what had definitively become “her side.”

“Don’t be silly, nii-chan,” she returned, though her voice chimed with a little humbly pleased giggle. “You’re working really hard on your homework,” she said as she got comfortable.

“Yeah,” said Tanjirou with a sigh. “My last test scores were good, so I’m doing a lot better. This is hard, though.”

“You’ll do fine,” she said encouragingly. “Is it okay if I turn off the ceiling light?”

“Yeah, of course,” he said, closing the book and putting it on the night stand. He forgot to mark his page.

“You don’t have to go to bed,” said Nezuko quickly.

“I don’t want to keep you up.”

“Just the table lamp won’t keep me awake,” she said. “Don’t worry—you know I’m a heavy sleeper.”

Tanjirou hummed. He didn’t want to keep reading the book. It sucked, and regardless, he wanted to snuggle up to Nezuko.

“My head hurts from reading so much,” he said, which was true. “I’ll go to bed with you.”

“Okay.”

They smiled at each other as Tanjirou flicked off the lamp and settled down into bed, facing her. He was blessed to sleep with her every night now, and didn’t think he could any longer sleep without her. He worried even more that she couldn’t sleep without him, with the way she needed him to comfort her in the middle of the night. He dreaded the looming arrival of their great-uncle returning from business. Sakonji had been gone a long time now, so it was bound to be sooner rather than later, and he didn’t know how he would survive for however many days the man remained at home and he and Nezuko would need to be separated.

For now, however, she was here, and he wasted no time in pulling her into his arms. Nezuko snuggled against him with a little gasp. Not only did they share a bed every night, but spent the whole night wrapped up in each other, clinging and snuggling and needing each other’s touch to feel relaxed. He held her sweetly, petting her hair, that feeling of absolute safety enveloping Nezuko’s body as she nuzzled her face into his shoulder, smelling the soap he used that calmed her down at night.

Things didn’t stay light for long, though, as Tanjirou tipped a hand under her chin to kiss her. They breathed into each other, constantly consumed by a terrible longing to be as attached as possible. Tanjirou never wanted her to doubt his feelings or his devotion to her, and couldn’t keep himself away from her, anyway—she was too precious, too needed, and by now he was spoiled, feeling he deserved complete access to her at all times. Nezuko didn’t mind; being swept up by him had become necessary for her to feel whole, protected, and loved. Never had she doubted his love before, but now it was essential that she experience it completely—regularly, for health and survival.

He slid his tongue into her mouth, stroking her hair as he devoured her lips and caressed her tongue without abandon. Nezuko gave herself over, melting as though being absorbed into him. She loved kissing him—could kiss him for hours on end—and by now, there were occasions where they practically had. His hand went to the small of her back, fingers creeping up beneath her shirt to touch bare skin; she shivered, turned on, but suddenly flooded with embarrassment. Her friend Minako had been dating her boyfriend for nearly three months now, and had still hardly allowed him to second base.

Decisively, Nezuko turned away from her brother, rolling onto her side and hiding her burning face.

“I’m sleepy, nii-chan,” she lied, mind racing.

Tanjirou, in a daze, only wrapped his arms around her from behind and snuggled into her as the big spoon, fixated on her like he was under an enchantment. It wouldn’t be far from the truth, the way he was addicted to her.

“You’re an angel, Nezuko,” Tanjirou mumbled, rubbing her shoulder and then tracing the length of her arm. He brought his hand to her hip and squeezed, pulling her ass against his groin and pressing his body against hers.

Nezuko gasped, breathing heavily into the pillow. His hands trailed lightly, teasingly, over her stomach and sliding up beneath the fabric of her shirt to cup her breasts with greedy hands, kneading them. He kissed her shoulder and the back of her neck repeatedly, nudging her tangled hair away with his nose. His lips trailed up to her ear where he licked along the edge of it—something he found she terribly liked, with the way she always squealed when he did it—his hot breath giving her cold shivers and reverberating in her skull.

“You’re perfect. I love you. I want you so much,” he whispered, unable to control himself from spilling everything, the soft words so loud and commanding. He did this to her all the time, absolutely driving her crazy with wanting him to be a part of her.

“Nii-chan…” she gasped, her mind racing and her heart pounding. She swallowed thickly, trying to catch her breath. No matter how much her blood was screaming, she just couldn’t say she wanted him to take her. She had no idea why, but this proved to be a breaking point. “Make me,” she whispered.

“What?”

“Make me,” she repeated, her face and body on fire, so warm in his arms and quivering beneath his hands where he played with her breasts.

Tanjirou stopped touching her and pulled back, his mind a mess of confused thoughts that he tried to scramble back together from where they had been consumed by nothing but the taste, feel, and smell of her.

“What—What do you mean?” he panted.

Nezuko’s face burned as she rubbed it into the pillow, unable to look at him in her shame.

“Make me have sex with you,” she squeaked out.

Tanjirou’s brain broke. He attempted to assemble the shattered pieces.

“What—Nezuko—I can’t do that to you,” he said, shaken.

She whined, squeezing her eyes shut.

“I can’t—I can’t ask,” she said. “So make me.”

“Isn’t… Isn't saying that the same as you asking?”

He sought any kind of clarification for her bizarre—and somewhat concerning—request. The confusion, arousal, and horror was not something that Tanjirou could put into words, even mentally to himself. He wanted to have sex with Nezuko—more than anything, especially in the moment, where he hardly had blood in his brain (which was probably affecting his thinking) since it had all rushed to his cock. But Nezuko was telling him to put himself inside of her as if against her wishes. But… Isn’t that the same as her asking? Was this some kind of strange fantasy she had? Was this how it was supposed to go?

It was once again confusing, arousing, and horrifying.

“Nezuko—What—What are you talking about?”

Nezuko shook her head, wrapping her arms around the pillow for comfort. She whined in frustration.

“I can’t ask, because that means I’m a slut.”

He wanted to laugh, but was too overwhelmed and bewildered.

“N-No—How?” he stuttered, his brain malfunctioning. “No, it doesn’t.”

“The girls at school would think so. I can’t tell you I want to, so just make me, nii-chan.”

“How—How is that better?”

What should I do?

“You want to make love to me, right?” her voice wavered in a simultaneously timid and demanding manner into the pillow, nearly losing her ability to speak in her own frustration.

Yes—Of course—Yes, I very much want to have sex with you, but—”

“Then make me,” she begged, not wanting to have to repeat it again.

Tanjirou reeled, head full of pressure but brain empty of coherent thoughts. Her request was bizarre, especially as she was proclaiming she wanted him to do something without permission. But it all was the same, right, no matter how she framed it? For whatever reason he couldn’t comprehend, other than it seemed to have something to do with the way she viewed herself, she wanted them to be intimate. He thought about it while she pressed herself into the bed, facing away from him. The plain, painful truth was that for however much she wanted this (seemed to want this—he kept trying to understand her wishes), he wanted her three times as badly, or at least it felt that way to him. He was put in a situation where he didn’t think he could say no, even if Nezuko was insisting she wasn’t asking a question. He breathed hard, and his hands shook. I want her… More than anything…

Finally, he leaned into her again, snuggling against her and wrapping his arms around her to hold her. She felt so good like this. He wanted to feel her in every way. He took heavy breaths and made an important declaration in her ear.

“If I’m going to do this, I need you to promise me that you’ll tell me to stop if you want to,” he said, firmly as he could, still half unable to believe he was saying this. But it was a necessary condition of his agreement. He would hate himself if he ever somehow hurt her, and she needed to know that.

She nodded.

“Yes,” she breathed, turning over her shoulder to look him straight in the eyes with as much intensity as she could muster in her overwhelmed state. “I promise.”

After all, she could easily say no. It was saying yes that was the problem. She wanted to give herself to him, and this was the only way—to also give up control, to let him be the one to make the decision for her.

“I love you, Nezuko,” he said protectively, even though he was the one about to claim her virginity. They passed a long quiet moment where she was only held in his strong arms that always sheltered her.

“I love you too, nii-chan,” she said.

Tanjirou’s skin burned. He knew what he wanted to do—what it seemed Nezuko wanted him to do—but he still grappled with if he should do it. He sighed, then kissed her neck.

The first order of business was that he wanted to see her naked, having only ever been able to briefly witness parts of her at a time before, depending on what act they were participating in. Her breasts were perfect; her pussy was perfect; and he wanted to see all of her at once, in her full glory. His cock twitched as he imagined how her perfect body looked on full display. Quickly—he was jittery, too—he hooked his fingers under the waistband of her pajama pants, reassuring himself that she promised to tell him to stop if she wanted. Trying to calm himself, he worked to get them down her thighs and pull them off her legs, then kicked them to the floor while he palmed her ass. She sucked in a breath at the same time—he hesitated—but she didn’t say to stop, so he repeated the process with her panties. God, he was hard as a rock, his head pounding between his ears. He gently traced his fingertips back up her body over her curves to her waist.

He glided his hand up further, opening up his palm to feel her smooth, taut stomach, her sternum, her breasts; he pinched one of her nipples, unable to stop playing with it like a typical teenage boy who simply loved boobies—he did love her boobies—and kissed her shoulder again, squeezing her breast more roughly in excitement when she whined.

The hem of her pajama top was next. He began shifting it up; she moved to make it easier for him, but he noticed she trembled.

“Nezuko…” he began, stopping.

“Nii-chan.”

Her voice was breathy, plain, but queerly assertive. He swallowed and helped her pull the top over her head, carefully discarding it on the floor, like he was afraid to drop it. Want and worry warred with him, as he was both ready to claim her body and frightened to upset her. Want sped him up, while anxiety slowed him down. This was disorienting, but, he realized, looking up and down Nezuko’s naked body, though she remained turned away from him, she trusted him. Nezuko was mature, and she trusted him fully, or she wouldn’t have even put the alarming request to him—he still wasn’t sure if it was a question or a statement, but kept arriving at the conclusion that it was the same thing. There was an utter faith from her that he would keep her safe, and he fully returned the sentiment; the most perfect mutual trust either could fathom. So she wanted this, and he should give in for her. It wasn’t difficult anymore once he made that conclusion, hypnotized by the sensual curve of her back and ass. She’ll be all mine… right now… not anybody else’s… no one ever touching her but me…

Nezuko’s body shook, goosepimples running up and down her legs though it wasn’t cold, as she waited for Tanjirou’s hands to return to her. She wasn’t afraid—it made her proud to acknowledge—but anticipation was high. What will it feel like? She wanted to know. All judgments aside, if she could forget them, she wanted to fully be with her beloved older brother. She twitched when his fingers brushed her hair aside and trailed over her bare shoulder.

“I’ll get undressed now too,” said Tanjirou, though she had no requirement that he talk her through it. She just wanted it to happen. She closed her eyes, shivering, shifting her legs which hid her sensitive center; in hiding, even an arm was draped across her breasts.

Taking a sharp inhale, Tanjirou stood up and pulled his t-shirt over his head, struggling when it got caught on one of his earrings. He supposed he was nervous too. Then he pulled down and stepped out of his plaid pajama pants before crawling back onto the bed toward Nezuko, hyperaware that his throbbing hardness approached her virgin body just the same. Holding his breath—his breathing had been erratic and uneven since she first told him to take her—he pressed his body to hers from behind, holding her as he always did. They both gasped, as for the first time they became entwined in a state of entirely bare skin on bare skin. Tanjirou’s erection pressed into Nezuko’s back, hard and warm. It twitched when it made contact with her. He hid his face in her hair, and she hid her face in the pillow.

“Nii-chan…” came her soft voice.

“What is it?” he asked quickly, frenetic with a mess of feelings at the prospect that she had changed her mind.

But she simply shook her head, unable to communicate with words.

It concerned him that she wouldn’t face him, but he wanted to kiss her, so he let go of his own innocence and demandingly brought a hand to her chin and turned her toward him, witnessing the brief impassioned glow of her eyes in the dark room as their lips met. Kissing while naked proved to be more electrifying than either of them could have predicted, and they moaned at the same time; Tanjirou’s grip on Nezuko’s chin tightened as he clutched her mouth close for him to feed on. Nezuko let him take a rough kiss, parting her lips with no defense as he pried them open, seeking her. Her mind had already solidified with the decision that she would let him do whatever he wanted to her. She knew instantly that beyond that, she would like it—whatever he wanted to do. She loved the feeling of him already, and the headrush of this perfectly romantic kiss. Swept away, she moved her lips and tongue with his, dancing ecstatically.

Tanjirou released her chin without breaking the kiss and brought his rough hand to a breast, his fingers brushing past a budded nipple before he cupped it. He was already greedy, the way he was slowly letting go of his reservations as their love making developed, and squeezed the soft flesh until she whined.

I’ll make Nezuko feel good.

He made it his primary mission, no matter how overwhelming his own desires were.

He sucked and pulled at her lips as he fully pulled her against him with his other arm around her too, holding her, and captured both breasts now, caressing their shape and pinching her nipples between his fingertips, thinking she was the most beautiful thing on earth beneath his hands. Her ass pressed against his cock was maddening. Bliss had Nezuko senseless, to the point she didn’t even register when his fingers had moved to stroke her folds between her legs.

She had let him do this before, just as she had let him put his mouth there, but embarrassment and some shame still flooded to her face, thinking how she must be such a bad girl to let her brother do this to her. The sentiment escalated when he gently slipped a finger inside and she gasped at the light penetration, squirming. Tanjirou fought the urge to ask her if she was alright, instead focusing on gliding his finger in and out of her with the help of her slickness, applying the perfect level of pressure to the best of his learned ability. Nezuko broke their kiss with a cry, turning her face away from him as it contorted into pleasure. Her heart pounded as he fucked her with his finger, her own delicate fingers clutching at the sheets, mumbling nii-chan in waves into the pillow to muffle her noises.

Tanjirou quickened his finger, groaning into her neck where he inhaled the fresh scent of her hair. This was all he had been able to get away with in terms of penetration so far, and knowing that putting himself fully inside was on the quickly dawning horizon, his own brain swelled with dizzying pleasure of desire.

“I want you, Nezuko. I want you.”

It could never purely be lust.

“I love you,” he said with a kiss on her neck as he slipped a second finger in. Nezuko yelped, her tightness expanding with pressure against the new fullness, soft inner walls stroked by every ridge of his fingers. Was this what it would feel like, she thought, mind racing as he guided her body through the journey of her first time. The sensation was exhilarating as he pumped his fingers at a firm even speed, the digits claiming her in their own way. She fought herself on the feeling, but she wanted it—wanted more of it.

I want to feel nii-chan, the thought crossed her mind, along with a million tumbling others, including the turn of the thought: I want nii-chan to feel me.

“Nezuko,” Tanjirou repeated her name in between kisses on her neck while he moved his hand, the other one massaging one of her breasts. Inexperienced, he licked and sucked on the skin where her throat met her shoulder, unaware that he would leave an embarrassing mark. He lightly dragged his teeth across her smooth tortured skin, wanting to consume her, and being completely consumed by the gravitational pull of his mind and body—and soul—to hers. She felt so perfect inside, so hot and wet, and he wanted to slide his cock into her with every fiber of his being down to the marrow of his bones. He needed to fully have her, to be part of her, to know her in that forbidden way he was so afraid for so long that he would never be able to. There was not a thought in his mind now that she wasn’t meant for him like this, that old grief blinked out of existence as if he had never even conceived of it.

Nezuko panted, heat and electricity surging through her veins from the flush on her face to where he lavished her shoulder with rough sucking kisses, down to her core to where his fingers thrust in and out in a rhythm that set the cadence of her breath. I’m ready, she found herself thinking, right as Tanjirou, as though reading her mind, slid his index and middle finger out from her, trailing some of her juices along her inner thigh. She didn’t have to question what was happening; he was ready too. She hoped he wouldn’t speak—she preferred the heated silence, other than the romantic praises and her name that he chanted back to her. Tanjirou didn’t say anything, simply pulled his hands and mouth away from her and reached over to open the side table drawer and pull out a condom. They both heard the pivotal crinkling of the packaging as he opened it, a sense of emotional and aroused whiplash hitting the both of them all at once with the deadening thought that this was happening.

Nezuko breathed heavily, and Tanjirou unrolled the condom snugly onto his pulsing hard cock. She buried her face in the pillow, fingers still clutching at the sheets, her ebony hair draped over her thin form, making lace patterns on her body and the bed. With the condom on, Tanjirou adjusted himself behind her, the two of them lying on their sides. Not only did her body look gorgeous, waiting for him, but she smelled incredible—the combination of her normal floral strawberry scent from her beauty products, and a heightened sense of her signature personal smell, too abstract to describe, added with what he could vaguely process were pheromones of lasciviousness and longing. The scents drew him in, setting him firmly on course to make her his.

Softly he trailed the backs of his fingers down her arm as he laid beside her, watching her shiver, and then pulled her flush against him, hearing her gasp. Then, his hand now gripping her hip, he shifted her so that he could focus on guiding himself in. She opened up more easily for him than expected, her walls having been prepared to part with the work he did with his fingers, as well as the way she was positively drenched, entirely primed for accepting him. He nudged her thighs further apart with his own, and Nezuko cried out as he pushed fully in.

“Nii-chan!” she gasped as though there wasn't any air, nails scraping against the fabric of the sheets she held onto for some kind of submissive control.

“Nezuko,” he returned with his own loud groan when he finally felt all of her, made himself one with her in the way their bodies fit together.

She whined while he gently drew himself out and thrust in again. His eyes closed in bliss, absorbing the exact shape of the way she squeezed him, wanting to memorize it as he was mesmerized by this moment. Nezuko’s body naturally fought him before relaxing as she got used to the movements.

Nii-chan and I are connected…

It was both a thought and a feeling, washing over her with every thrust. She was unable to stop the sounds that were coming out of her, moans and whines and grunts. The sounds were desperate and adorable to Tanjirou, loving to hear her make these noises for him in response to what he was doing to her, exactly what he had wanted to do for as long as he had known whatever it was that told him how his love for her had expanded beyond anything he could ever imagine. Knowing he loved her so much that he was in love with her.

She felt so good, her cunt so tight, that it would be so easy to forget about everything else and blank out to consciousness beyond the way he grinded himself against her walls, swaying in and out of her—but he didn’t want to leave her wanting where he had already been building her up to an orgasm with the pressure of his fingers inside, so he reached in front of her to stroke her folds until he found her clit.

Nezuko gasped as the pressure came upon her there, twitching as her cunt once again wrapped around his cock during another thrust at the same time. She called for him in a broken voice, hearing him only groan in response while he stopped moving and let himself be fully embraced by her core, settling into that beautiful oneness with her. Careful, he massaged the sensitive nub, swirling around it with the tip of his finger. He was gentle with her there, understanding how vulnerable the tiny bundle of flesh was—but he was also relentless, knowing if he took the pressure off that it would derail her journey to orgasm. Nezuko whined, wetter than she had ever been, more turned on than she had ever been, at a point where she was incapable of perceiving anything but the sensations—and that they were coming from the way Tanjirou touched her.

It was almost too much, his finger on her clit while he was inside of her, the sensation of being stimulated in two ways at the same time—nearly a feeling of being penetrated twice simultaneously, though she couldn’t even imagine such a thing. While the size and depth of his cock somewhat hurt, the way he pleased her as he had learned how was ecstasy, and enhanced by the way he filled her—and he hadn’t taken himself out, only pressing hard against her so that the tip of his cock maintained pressure on her cervix. She felt his breath on her neck as he kissed and mouthed her skin at the place on her shoulder where he had already started unknowingly forming a bruise. The combination of sensations sent a tingling feeling down her spine and arms to her fingers where she clutched at the sheets. Being entirely consumed by her precious older brother was divine (I love him, I love him); though the back of her brain still licked at her that she was bad for this.

Nii-chan and I are connected…

Tanjirou had learned to get her off with his fingers after touching her over the past few weeks—how exactly she liked to be stroked, and how much pressure; and she had felt dirty, dirty for letting him make her come, while simultaneously living in ecstasy of the intoxication of what it was like being so intimate with him. Everything in her body told her it was right, and she felt safe with Tanjirou, but her mind kept shoving back with shameful criticisms. She moaned as the pressure built up higher when the rough pad of his fingertip wound circles over her clit. She let all the thoughts go but the ones that spoke to her of love.

Nii-chan and I are connected…

Tanjirou carefully drew himself out and began fucking her softly again, gasping each time he slid fully inside, moaning as he slowly pulled out, and then another harsher sound as he pushed back in.

I’m so close to Nezuko…

No one else would ever touch her like this. No one else would ever have her like this. He had never wanted to share her with anyone from the beginning, before he was even old enough to realize his feelings—his perfect little sister that no one else deserved—and now he would never have to. She belonged all to him, only to him. Even with the condom, he could feel her melting and tightening around him.

“Mine, Nezuko,” he whispered gently.

The moan he let out when he bottomed out within her again was almost guttural.

“Nezuko…” he choked out as he pressed hard into her, fully inside—he couldn’t stop repeating her name.

Nezuko was a squealing and whining mess, tears in the corners of her eyes from all the sensations, but not wanting any of it to stop. Her body burned, wet heat between her legs where she held him—so full—responding to each of the swirls of his finger on her clit and his gentle movements inside of her, softly rocking back and forth. Her head was also full, as if with a tenderly burning golden light, and her voice cracked in the middle of a moan as she came hard on his cock.

“Nii-chan…” she moaned, a single tear breaking away from her misty eyes. What was this bliss?

He knew he had taken her over the edge, a happy kind of pride spreading through his chest, his heart glad that he had achieved his goal of her body receiving the same amount of pleasure from this as his would. And he was breaking down. She was too wonderful, too tight, and the stroking of his cock by her cunt was too ecstatic, sizzling all his blood and electrifying every nerve ending.

“Nezuko… I’m…”

His quick, heavy breaths increased in pace as he gripped her hip with the hand that had been pleasuring her, squeezing her waist and also speeding up the pace of his movements. The act had them both shaking, and Nezuko was calling out louder now, with no idea how she was taking him with this more intense vigor. Her body was still tingly with orgasm, and by now had entirely embraced the feeling of him inside her, accepting him as a part of her he was made for. Tanjirou lost himself to this succession of final thrusts, choking out her name as he came.

Everything went white until he was brought back by the sound of Nezuko’s whimpers and the quaking of her body against him. He snapped back to attention, some pangs of anxiety hitting him through the afterglow of his orgasm. He quickly pulled out of her, as though he had been unwelcome, and then got up to discard the condom in the small wastebasket in the corner of his room. He cursed having to do it; his only thought was returning back to connection with Nezuko. When he turned to look at her on the bed, he saw that she was hugging herself and wiping her eyes. He hurried back and swept her into his arms. Nezuko finally faced him and snuggled into his chest. Bare skin on bare skin—slightly damp with sweat—prolonged the lingering feelings of deep closeness, that sense of being one still enclosing them in a golden bubble. Tanjirou stroked her hair, his other arm squeezing her against his chest for a long moment.

“Are you okay, Nezuko?” he asked as he cradled her face with both hands, his thumbs brushing softly over her cheekbones where there could be found only the slightest remnant of tears. She was breathless, but not in pain or afraid. She was only in love, and wanted him to know.

“Yes,” she said simply, hoping the way she melted into his eyes with perfect trust would allow him to believe her.

He kissed her forehead, briefly her lips, then her chin, all over and all over again.

“Did I hurt you?”

It was his worst fear, and though he felt so full of love, his heart hammered with anxiety, worrying the experience had been too much for her. He had tried his best to be careful, but now that it was over, he felt like he couldn’t even remember anything other than the passion and pleasure.

“No, nii-chan,” said Nezuko, putting her own hand over his hand that laid on her cheek. She nuzzled against his hardened palm, begging her heart to calm down, but it wouldn’t stop pounding any more than his would.

“Was I too rough?” he asked, sure he had done something wrong and prayed that he hadn’t. He couldn’t bear the thought of having upset his precious girl at all, especially with the particular way she had requested he take her virginity.

“No, you weren’t,” said Nezuko, staring hard at him. Her body trembled, and though she wasn’t cold, she needed his heat, so she pressed herself into him, still curiously settling into the way their fully naked bodies felt together. “I promise. I would’ve told you.”

He nodded twice, then kissed her softly on the lips. She could hear his heart beating now, and wondered if he could hear hers. The hardness of his naked chest felt amazing against her breasts, and his arms embracing her bare back refused her light-headedness to leave.

“Did you like it?” he whispered then, hoping the question wasn’t going to make her uncomfortable, since he was finally beginning to put together the pieces that allowing and enjoying sex was what was making her hesitant in the first place.

Nezuko’s cheeks couldn’t be more flushed than they already were, but they burned as she rubbed her nose in between his pecks.

“Yes,” she said quietly, letting it be known between them. “Being so close to you is all I could ever want, nii-chan.”

Tanjirou let out a breath of relief, his exhale tickling her hairline.

“Me too,” he said, releasing all his stress. “More than anything, I feel happy.”

“Me too,” said Nezuko, smiling, her lips pressed against his skin.

Tanjirou placed a kiss on her forehead, lingering there. There was nothing more glorious he could imagine than laying there fully entwined with her as he was, absolutely nothing between them, not even the flimsiest piece of cloth or difficult word.

“I love you,” he said, holding her tight. “You are the most precious thing to me in the entire world. You are my world. You’re mine forever.”

Nezuko kept her eyes closed in bliss, safe in the way his embrace caged her.

“I love you too, nii-chan. I never want to be apart from you.”

“We won’t be,” said Tanjirou. “Not until the end of time.”

“I love you,” said Nezuko again.

“I love you too.”

Neither of them knew what time it was, their intimacy having felt like it was an eternity of living in Heaven. Tanjirou therefore assumed it must be very late. It surprised him when the alarm clock showed that only just over a half hour had passed. Still, it was a school night. Anything as mundane as classes felt like it belonged in another universe compared to the state they were in.

“Nezuko… would you sleep naked with me?”

A tremble passed over her, but truthfully she didn’t want this blending of her body with Tanjirou’s to stop, even if part of her felt it would be more proper for her to put on her clothes. She supposed that regardless of how tight her mind had held onto her reservations before, there was no need for them anymore. She and Tanjirou had gone all the way with their intimacy—more boundaries had been crossed than just the base physical one; their relationship couldn’t be any more gone from the one of normal and accepted sibling behavior. She didn’t regret it, but she was still overemotional in the moment, and processing.

She agreed in a quiet voice, and Tanjirou sighed in relief. Not only did he not want to separate himself from Nezuko any more than he already had, he didn’t think he could, as if he truly wouldn’t survive the absence of her bare skin. His need for her hadn’t ended with orgasm. He had to feel her completely forever, and he thought without the warmth of her naked body on his at the moment, he would freeze.

“I love you so much, Nezuko,” he said, just holding her and inhaling her scent, which still carried faint traces of lustful pheromones. “I wouldn’t want to live without you.”

“Nii-chan… don’t say that.”

Fragmented memories from the tragedy of the car accident jabbed at her like fractured glass, piercing her all over with fear, panic, and dread. She had almost died. Why everyone else but her lost their lives, she could never know—and the survivor’s guilt was brutal. To imagine anything like that ever happening again was devastating on its own.

“I mean it, though,” said Tanjirou, his voice tightening as tears came to his eyes. “I can’t be without you at all. If I had lost you…”

“Don’t talk about it, nii-chan,” said Nezuko, her eyes stinging in an unpleasant way that wasn’t at all like the passionate tears she had experienced during their lovemaking.

“I’m sorry,” he said, holding her with the utmost tenderness, as she was cherished, and as though she was fragile. “I just couldn’t help the thought coming to my head. You’re my everything, Nezuko. I can’t ever let you get hurt or taken away.”

She shushed him, running her fingers through his thick messy hair now. 

“Just like you said, we won’t ever be apart.”

He nodded, then gave her another kiss that took her breath away. He met her open-mouthed immediately, finding her tongue and meeting it with all kinds of caresses as their heads filled up with the warmth of connection again. Her body still hadn’t forgotten how he felt inside her, and the kiss enhanced the memory. She thought she might pass out when she realized she would want him again, if she thought her body could handle that; but upon decent reflection she found herself certain she couldn’t take him again at the moment.

They whispered their I love you’s again as they broke apart, just staring at each other and holding on tight.

“Now I really am sleepy,” Nezuko whispered. In perfect time, she yawned. Tanjirou chuckled.

“Yeah. I am too. And we do have school tomorrow,” he said regretfully.

Nezuko heard his tone, and returned the resentment.

“I don’t want to go,” said Nezuko. “I want to stay with you all day.”

She snuggled into him like a stubborn child. Tanjirou’s heart leapt.

“If we did that, it would ruin your perfect attendance,” he reminded her. Of course he wanted her all to himself, but he didn’t want her to give up anything that made her fulfilled and happy on her own.

“Maybe just one day is okay,” she said. After all they had done, at that moment she felt young. It was just a dichotomy she would have to learn to live with, she thought: both the romantic partner and the little sister. “To stay with you.”

Tanjirou smiled and tucked her hair behind her ear.

“It would make me very happy to stay home all day with you, Nezuko.”

Despite how much effort he was putting in to improve his school performance, he truly didn’t give a damn about his attendance at the moment. He thought Gyutaro would be proud.

“We can do that, then,” she said, giddy despite her sleepiness.

He wrapped her up close and tucked her head beneath his chin, and the exhaustion set in for both of them.

“I don’t even want to leave you to sleep,” said Tanjirou.

Nezuko hummed happily, hugging him tight.

“I don’t either. But we’ll be together. We’ll sleep together. Always together now.”

“Yeah,” said Tanjirou, petting her. “Always together.”

Notes:

i really had fun with this and was glad i got to write this despite Through the Open Window only being a rated M fic, so thank you to all the readers who voted for it! i don’t regret my rating decisions—i had my goals for TtOW and i think i achieved them—but still, like i said, it was fun to finally imagine Tanjirou and Nezuko’s first time. i set it up in TtOW too, so i hope everyone caught that and liked it, even though this might seem a strange route. i didn’t want to write a typical generic missionary first time, so i tried something different.

anyways, i’m rambling ‘cus it’s been a while. this concludes everything i have for the KA AU at the moment! it sadly also concludes what i have coming for NezuTan content in general, other than maybe another smut oneshot that happens when Nezuko is still a demon. i have a fic for another fandom to work on, and i’ve just written so much NezuTan (please check out all my content if you haven’t!) that i’m a little burnt out and out of ideas for the moment! if you have any, feel free to leave them in the comments or send them to me on my tumblr, sad-girl-poetry.

thank you for reading and sayonara! xog ♡

ps; i love comments. what was the hottest part? ;o

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