My Little Sister Is the Best F*p Material - Volume 6 Chapter 07: Sex Between Onii-chan and Sister

Volume 6 Chapter 07: Sex Between Onii-chan and Sister

Having somehow managed to finish a massive parfait—stacked with bananas and whipped cream, easily fifty centimeters tall—by shoving spoonfuls into each other’s mouths with Yuka, I dragged my heavy stomach back home. When I opened the door, the cool air filled the entrance, and the familiar comfort of my family home instantly calmed my heart. Even just spending one night in an unfamiliar environment can be exhausting.

“Welcome back, Onii-chan.”

Miyu greeted me, emerging from the living room in my hand-me-down clothes, which she’d fully adopted as her indoor wear. The fabric, slightly lifted by the swell of her breasts, fluttered around her stomach. She paired it with short shorts, leaving her lower half almost entirely bare.

To put it simply, she was just wearing an oversized T-shirt, but why did this little sister of mine look so damn erotic? No, I shouldn’t think that. After my date with Yuka, I’ve grown as a man. I need to show Miyu that, too.

“Sorry for suddenly staying out last night. But I managed to solve Yuka’s problem.”

As I took off my shoes and stepped inside, I handed Miyu the souvenir Yuka had given me—a standard box of crunch chocolates themed after the amusement park’s mascot.

“Good. I knew I could count on you, Onii-chan.”

Miyu gave me a relieved smile. Unlike others, I’d managed to solve something for Yuka that Miyu couldn’t. Maybe I could take a bit of pride in that.

“Gonna take a shower?”

“Yeah, I’ll freshen up.”

I’d showered with Yuka multiple times, but I’d worked up a sweat on the way here, and more than that, I felt reluctant to touch Miyu with a body that had just been to a love hotel with another girl. When I got out of the bathroom, a fresh set of clothes was neatly prepared in the changing area. I thanked Miyu’s thoughtfulness in my head as I returned to the living room.

Miyu was sitting on the sofa, munching on the souvenir from Yuka. What a cute creature. I grabbed a bottle of tea from the fridge, took two glasses, and sat on the sofa.

“Want some tea?”

Miyu nodded silently. I poured tea into a glass for her, then into my own, and took a sip to quench my throat.

After eating a few pieces, Miyu closed the snack box. I patted my lap to ask if she wanted to sit there, and she stood up, straightened her posture, and plopped down daintily. In front of me was her glossy black hair, reaching down to her waist. It was always so well-maintained and beautiful. And it smelled amazing.

When I complimented Yuka’s hair down, she said, “It’s because Miyu’s is straight, right?” I denied it, but she’d hit the nail on the head. If Miyu wore twin-tails every day, I’d probably be into twin-tails. I love straight hair because I’m so used to Miyu’s long, straight locks.

…Wait, looking closely, her hair doesn’t quite reach her waist anymore.

“Did you cut it?”

“During summer break, I’ve been curling or extending it a lot. Also, I secretly added some pink highlights on the inner layers.”

When Miyu brushed her hair aside, I could see thin streaks of pink woven in.

“You’re okay with it being so subtle?”

“I’d love to do more, but I thought people like you might see it as delinquent culture, so I just added extensions that aren’t visible from the outside for now.”

I see, so it’s not dyed, just extensions. But knowing Miyu, who’s obsessed with lolita fashion, she probably wants to dye her hair for real during long breaks.

“What’s the furthest you’d want to go?”

“I’d love to dye it all ash gray and add blue streaks.”

“Whoa.”

That’s pretty bold. It’s a classic lolita color scheme, and I’m sure Miyu would pull it off perfectly.

“But I don’t want to lose my natural black, so I’m not planning to dye it.”

“Got it. It’s your hair, so do what you want. But I’m glad you feel that way.”

No matter how compatible two people are, it’s rare for their values to align perfectly. The reason I’ve never felt uncomfortable with Miyu is because she’s always considerate of me.

“You’re such a hard worker, Miyu. It’s impressive.”

I murmured while running my fingers through her tangle-free hair. It’s obvious, but I wanted to properly praise her with words.

Being able to work hard at what you love isn’t a common talent. Miyu pursues what she wants, does what she needs to, and her drive is something I need to learn from.

“Like what, for example?”

“Your beauty routine, your studies, your sewing—you work hard at all of it. Being around you makes me feel like I need to step up, too.”

Miyu responded with a flat “Hmm” and glanced at me briefly. I guess my praise was kind of lame. I need to focus more on her inner qualities.

“You’re always so calm, but you’re subtly kind in ways I really appreciate. You’re full of emotion, in a way. You’re loyal to people, too.”

I could go on forever about what I love about Miyu. Still, it’s hard to pinpoint what would make her happy to hear. If possible, I want to express things only I’d notice because we’re so close.

“Hm.”

Miyu lifted her chin, locked eyes with me, and blinked rapidly.

“What’s with you all of a sudden?”

“Oh, uh, I’m not great at voicing my thoughts, so I wanted to make sure I said it out loud.”

When I said that, Miyu kept her face tilted up, blinked slowly once instead of nodding, and then turned forward again.

“Was… that too weird?”

Her reaction was so muted that I asked nervously. Then, Miyu wrapped my arms around her waist like a belt and leaned back with her full weight.

“Did you think I wouldn’t be happy?”

She looked up at me with a smug grin. I’d been totally played.

“I was a little surprised to be praised out of nowhere.”

“I thought I’d gotten a bit better at handling girls, you know. I wanted to show you that, too.”

“Oh, really?”

Miyu leaned her back against my arms, stretched out her legs, and lay sideways. It was like I was holding her in a princess carry.

Then, she casually rubbed her bare legs together and stared at me. Without a word. My little sister, lying there in my shirt, rubbing her glossy thighs together and gazing at me.

Her adorable, teasing demeanor made my lower half swell uncontrollably. I’d wanted to assert my brotherly authority, but I was no match for this sister. She’s mastered the art of drawing out her feminine allure.

“Sorry, I haven’t changed at all.”

“You’d probably do fine with a shy girl, Onii-chan.”

Miyu knelt on the sofa, straddled me, unzipped my pants, and slipped both hands into my boxers.

“Oh… ooh…”

“The ones you’ll be dealing with from now on are me and Kanade-san. You can’t treat us like a pure maiden like Yuka.”

Miyu flaunted her ample cleavage while rubbing my penis back and forth like she was washing it. Maybe because I’m used to her blowjobs now, the unfamiliar sensation of her warm hands made my penis harden instantly.

“Girls who initiate erotic stuff themselves are rare, huh?”

“And a cute little sister, no less.”

Miyu added playfully. What an insanely erotic sister, straddling a guy and stroking his penis in broad daylight.

She might just be the most erotic sister in the world. Petite, baby-faced, hairless down there, yet with big breasts and plump thighs—she’s practically made of eroticism. I couldn’t help but want to make a naughty request.

“…Can I touch your boobs?”

I slipped my hand under her T-shirt and asked. Miyu gave me a look like, “I knew you’d say that,” but surprisingly responded positively.

“You can take off my bra.”

Though she’d been reluctant at first, once she experienced it, she seemed to accept it easily, suggesting she didn’t mind as much as she let on.

While enjoying her handjob, I reached for her bra’s clasp. To unhook it, I had to pull inward to release the metal, and even then, I could feel the weight of her breasts. I had nothing but respect for the bra supporting such magnificent assets.

When I unhooked it, her breasts, freed from the bra’s support, were pulled by gravity, and the shape of her perky nipples appeared through the T-shirt. Big breasts are just so erotic. I thought I’d grown a bit, but I stood no chance against their allure.

“The weight of your boobs is just… incredible.”

“Doesn’t Kanade-san’s have more?”

“It’s about density. Yamamoto-san’s are overwhelming, but yours have this… hefty feel.”

“They’re both fat, so the density’s the same.”

Miyu scolded me by squeezing my shaft from the base, forcing blood to the tip. I couldn’t see what was happening with her hands in my pants, but the sensation alone told me my glans was swollen to the max.

“It’s getting really hot down there.”

The more I kneaded Miyu’s breasts, the hotter my erection grew, as if her breasts were a pump drawing blood into it. My engorged penis became even more sensitive, its slick, precum-coated tip toyed with by Miyu’s fingers.

“Ugh… Miyu, your finger technique feels too good… You’re way too skilled…”

“I didn’t get this dexterous just for this, you know.”

Even as she said that, Miyu smugly continued to torment my cock. Her small hands meant the stimulation wasn’t dulled by her palms; each finger wrapped around me like a tentacle, teasing my sensitive spots with exquisite precision.

“Can I take off your T-shirt, too?”

“That would leave your little sister topless, you know…?”

Miyu responded to my request with an obvious question, perhaps out of consideration for my intelligence, which had apparently dropped to toddler levels.

“I want to rub your boobs while looking at your naked body.”

“Is that really something you should say to your actual sister?”

“No regrets. I’m already groping your boobs.”

When I showed my unwavering resolve, Miyu shot back with a biting, “You should get your head checked at a hospital someday,” before stripping off her bra and T-shirt.

Her breasts, previously lifted by her arms, jiggled as they fell free once she removed her clothes. The firm, youthful skin of her plump breasts and the slightly upturned nipples exuded a sense of weight just by looking at them.

“You’re beautiful, Miyu.”

I grabbed her breasts again, kneading them vigorously. When I applied pressure, my fingers sank in, only to be pushed back by their inner elasticity.

She’s petite, under 150 cm tall, with a bust over 90 cm. To think I’m getting a handjob while groping my little sister’s massive boobs—what greater happiness could there be in life?

The allure of big breasts isn’t just in their elasticity. Their prominence is key. Being able to caress the underside of her breasts with my entire palm is a privilege unique to large chests. Compressed by gravity, that area is smoother and glossier than even her buttocks. When I lifted them in place of her bra, gratitude welled up for their weight, soon turning into arousal.

“You’re really going at it, huh?”

“Well, yeah. How’s it feel to be touched like this?”

“Mmm… It actually… feels pretty good…”

Miyu showed no signs of discomfort as I fondled her chest. Unlike her usual teasing aloofness, she quietly let me play with her breasts while stroking my cock.

“Hey, Miyu.”

It’s all about the flow. It’s no different from casual conversation. How far you can go with something erotic isn’t about the relationship—it’s about the mood of the moment. I suddenly realized this.

“Can I suck on the tip?”

Normally, Miyu would instantly say, “No way.”

“Ugh… Hmm… What should I do?”

She was searching for a compromise. It wasn’t that she hated the idea of me sucking her breasts—her nipples were just too sensitive, making her hesitant.

“If you can last a minute without cumming, you can suck them.”

“Do there have to be conditions?”

“Your premature ejaculation needs some fixing, doesn’t it?”

Fair point. If I came too quickly, I wouldn’t be able to satisfy Miyu.

“Alright, one minute.”

But I had confidence in this challenge. The reason I cum so fast with her blowjobs is because our first sexual experience involved me ejaculating in her mouth and her swallowing it. My body’s conditioned to think that if Miyu’s mouth is nearby, that’s where my semen belongs, making it impossible to hold back. But with a handjob, that ingrained memory is weaker, so I could endure.

“If I haven’t cum by the time the timer goes off, I’m sucking those boobs to my heart’s content.”

With that declaration, I stripped off my pants and underwear, set the timer on my phone, and hit start.

“Go ahead, do whatever you want.”

Miyu slipped two fingers into her mouth, coating them with saliva, then gripped my penis again.

“Ugh… Ah…!”

Her seductive gesture and the sudden shift in pleasure pushed my urge to cum to the brink in an instant. I clenched my abs and glutes, barely holding back, but Miyu smeared a makeshift lube of saliva and precum onto my cock, expertly teasing my pleasure spots with her slender fingers.

Her left index finger tickled the base of my shaft and balls, while her other fingers massaged my scrotum. I could feel precum leaking out so much I could sense it traveling through my urethra. Miyu’s right hand scooped it up, rubbing it into my glans, as if praising my horny body, making me want to surrender completely to her handjob.

“M-Miyu… Please… go easier on me…”

“You’re already making that face? It’s only been ten seconds.”

Miyu leaned forward on her knees, flaunting her bountiful breasts like a reward. With my view dominated by them, my pathetic cock was still being ravaged by her handjob.

“Maybe this’ll work better on you.”

She brought her hips so close that her kneecaps hit the sofa’s backrest, squeezing my cock with a tube-like grip and stroking it with a slick motion. Her hips moved up and down in sync with her strokes.

The wet, sloppy sound of her precum-soaked hand mimicked the sensation of having sex with her face-to-face. All I could see was Miyu’s naked body. Beyond her breasts, her exposed neck and collarbone strongly reminded me of her nudity.

The glimpse of her underarm, partially hidden by her sideboob, sparked a new sexual curiosity. From her delicate shoulders to her upper arms and elbows, it was all bare skin. Everywhere I looked was Miyu’s naked flesh. She was naked.

“Ugh… Haa…! M-Miyu…!”

Realizing my defeat, I desperately pinched my thighs to distract myself from the urge to cum. By diverting my focus from my pleasure zones and tensing up, I suppressed the ejaculation reflex. Twenty seconds left. I had to endure with everything I had.

“That’s cheating, Onii-chan. Your hands belong here.”

Miyu gently peeled my hands off my thighs and placed them on her breasts. Unconsciously, I started kneading them, knowing it was the opposite of holding back but unable to stop.

Pitying me, Miyu stroked my cock at a relentless pace, as if urging me to cum. Her cold gaze sent shivers of pleasure through my lower abdomen, finally igniting the fuse to my climax.

“Aah… No… I’m gonna cum…!”

I tilted my head back, curled my toes, and made a final stand. Even as pleasure pulsed through my brain, I visualized letting it flow out through the top of my head, barely holding on. And then, finally—

“Stop! Stop, Miyu!!”

I wrapped my arms around her, pinning her arms to stop her. Nearby, the alarm signaled that a minute had passed.

“Haa… Haa… I didn’t… cum, right…?”

I checked my lower half just to be sure, but there were no signs of ejaculation. I’d endured. I’d survived Miyu’s pleasure torture, a grueling minute of restraint, and earned the right to suck her boobs.

“Miyu, can I suck them now? Or lick them, or just devour them?”

When I voiced my uncontainable desire, Miyu looked down at me with a deadpan stare.

“Have you considered how your sister feels being told that by her actual brother?”

“I have.”

I haven’t.

“You haven’t, have you?”

“Nope.”

My mind was so consumed with her boobs that I couldn’t possibly think about her feelings.

“Then choose which boob you want to suck, left or right.”

“Right.”

“Oh, okay… You’re fine with just one?”

“I’ll suck the right one from my perspective first, then the right one from yours.”

“Ugh. Yuka’s been teaching you weird tricks, hasn’t she? Fine, do whatever you want.”

Miyu’s cold tone felt oddly pleasant. My lust surged. I’m hopeless when it comes to her.

“Here goes.”

I gently lifted her breast, stared at the peach-colored nipple, and, with gratitude, took it into my mouth.

“Nn…”

Miyu tried to stay silent, but her hyper-sensitive nipples couldn’t stay unresponsive. When I rolled her nipple with my tongue, her body twitched as if I were teasing her clit. She arched her back to escape the sensation, but having agreed to let me suck, she couldn’t resist and pressed her body closer to keep her breast in my mouth.

“Ah… Uu… Nya… Nn…!”

The texture of Miyu’s nipple was smooth. Her large breasts meant her nipples were substantial, with enough room to lick the tip even while holding the protrusion between my lips. I rolled her nipple with my tongue, savored the sensation, then sucked hard with a chuu.

“Nn… Nn, ah…!”

“Chup… Chu… Haa… Miyu…”

Sucking her breast filled my mouth with a sweet scent. It wasn’t milk—milk supposedly tastes metallic. What I felt was surely the scent of motherhood, a pheromone unique to women, not meant to seduce but to soothe.

“Ahh… Miyu…”

The scent melted my brain. Forget left or right—I wanted to suck her boobs forever.

“O-Onii-chan…! Nn, hya… Don’t… suck so hard…!”

As my consciousness faded, Miyu’s moans grew louder. I was probably sucking harder than I realized. Babies suck desperately to get milk, so of course I’d do the same.

But there was a clear difference between me and a baby. The more Miyu’s arousal grew, the stronger the scent in my mouth became. Unlike a baby, I had the intelligence to understand that the more naughty things I did to her, the more I could savor this brain-melting pheromone’s sweetness. So I sucked her breast, licked and teased it with my tongue, and used my free hand to pinch and stimulate her other nipple.

“Higyuu… Nn, ah…! Oni… Hyan… Nnya… Higii… Nn, ahh…!!”

Miyu’s legs trembled, her thighs pressed together, her body swaying as if she were on the verge of losing control. At first, she continued stroking me while I licked her nipples, but that soon stopped. Instead, she gripped my shoulders tightly, as if she couldn’t stay upright without it, overwhelmed by the pleasure.

Undeterred, I kept licking her nipples. Her lewd body arched with every swipe of my tongue, and I, feeling the full force of her femininity, rubbed my erect cock against her thighs.

“Mchu… Ahh… Mi… Miyu…!”

“Nhi… Iii… Nn, ah… Hihya…!!”

In the heat of rubbing my penis against her thigh, my erection pushed up against the front of her shorts. At that moment, Miyu convulsed with a shudder and clung to me, collapsing onto my chest.

It seemed she’d climaxed. Just having her nipples sucked had pushed her to her limit. A single brush against her clit had easily sent her over the edge.

“Haa… Haa… Sorry, I came…”

“Miyu, I want to cum, too.”

“Ugh… I know, I know…”

Exhausted, Miyu lazily stroked my penis with one hand. It wasn’t that she wanted to half-ass it—she probably didn’t have the energy for more. But for me, I wanted to cum while still sucking her breasts.

“Can you sit up a bit more?”

“Y-Yes…”

When I asked, Miyu, with slightly teary eyes, sat up and let me suck her breasts again. Her determination to keep her promise, even in this state, made me proud as her brother.

“Nn… Nnn… Ah…”

Miyu moaned as she jerked me off. Normally, her sultry, melting expression would drive me wild, but now, the oddly detached atmosphere was heightening my arousal.

“Ahh… Miyu… I might cum soon…”

My penis, already near its limit from groping her breasts, was ready to burst. As Miyu, limp and drooping, sucked on her nipple and stroked my near-exploding erection, the muscles for ejaculation contracted, signaling release.

“Ah… Ugh, I’m cumming…!”

Unlike my usual moans, it was a subdued ejaculation, but the volume was immense. My penis spurted thick, white semen repeatedly, coating Miyu’s hand and thighs, before finally shrinking, its mission complete.

“Ugh, you came so much… If any got on my shorts, you’re in trouble.”

Miyu grumbled resentfully as she checked the aftermath. Luckily—or unluckily—no semen had gotten on her clothes. She licked the cum off her hand, then wiped her thighs with a nearby tissue.

“…That should do it.”

After confirming she’d cleaned up, Miyu picked up her discarded clothes, straddled my lap again, and sat down. Right in front of me, she slipped her arms through her bra, nestled her ample flesh into the cups, and fastened the clasp.

“Done already?”

“You came, so you’re satisfied, right? Sucking on me like a baby.”

As Miyu put her clothes back on, she lifted my pants, which had been pooled around my ankles, so I quietly got dressed, too. Her prickly attitude was probably a way to hide her embarrassment. After all, during our little challenge, if Miyu had whispered “cum” in my ear, I wouldn’t have lasted a minute against her pleasure torture. It’s possible she weighed her pride and decided she wanted me to suck her breasts, at least a little.

“When can I suck them again?”

Unable to hide my desire, I asked her directly.

“That depends on Mama’s mood.”

Miyu answered, but saying it out loud seemed to embarrass her, and her eyes darted around for a moment.

Mama, huh? To think I have such a tiny, cute, busty little sister who’s also a “Mama”—my life really is blessed.

“Mama…”

Overwhelmed with euphoria, I hugged Miyu. Playing with her bare breasts was blissful, but hugging a woman while feeling her perfectly shaped breasts through her bra had its own charm. Miyu grabbed my shoulders firmly, pushed me back with the most pitying look of the day, and held me at arm’s length.

“No, seriously, Onii-chan, that’s just creepy.”

“I wasn’t expecting such a harsh reaction.”

She didn’t have to curse me out and act that grossed out. I’m her actual brother, after all.

“A guy who strips his sister, sucks her breasts like a baby, and calls her ‘Mama’ is creepy, isn’t he?”

“Uh, yeah…”

When she put it like that, it was undeniably true. I didn’t need her to spell it out. I thought I’d stepped up as a man through my boyfriend-like roles with Yamamoto-san and Yuka, but the core of a person doesn’t change so easily. Realizing that alone made all my efforts worthwhile.

“Whatever.”

Miyu patted my head gently, then turned and settled back between my knees. I love how she forgives me so easily, even after all this.

“On a serious note, what should I do if I want to suck your breasts during sex in the future?”

“Hmm… If I’m still rational, it’ll be on a permission basis.”

“And if you’re not rational?”

“Well, I guess you can do whatever you want.”

Seriously? I didn’t expect to get such a golden promise. It pays to ask. But future sex, huh? So Miyu’s already imagining those kinds of scenes—both of us, naked together.

“Hey, Miyu. About that thing we talked about before, the whole ‘going all the way’ thing…”

We need to settle this, too. Miyu craves my semen so intensely due to her biological instincts that if we had sex, she might lose control and try to conceive. It’s my responsibility to keep that from happening and manage her urges.

“I’ve gotten to know you pretty well, Miyu. Like when you get in a naughty mood or what makes you happy.”

Through our sexual encounters, I’ve made her feel good, been scolded by her, and sometimes seen her take the lead. I think I’ve figured out what triggers her reactions and what her true feelings are, more or less accurately.

“So, I think we can move forward and still enjoy sex together. I’ll make sure everything’s okay, and if something happens, I’ll work hard to take responsibility. So, uh…”

Trying to wrap it up neatly, I started losing track of my point. But there’s one thing I need to say.

“Should we have sex soon?”

Based on everything we’ve been through, Miyu should understand what I’m thinking. She listened quietly, without even glancing at my face.

“Okay. I’ll have sex with you, Onii-chan.”

Miyu took my hand and said it clearly. Those simple words carried a trust that wouldn’t have come without our bond. I was thrilled to realize we’d finally connected on this level.

“When?”

Her question made me pause. We just did it, so waiting might feel awkward, but doing it right now also seems like the right move.

“T-Tonight, maybe?”

After saying it, I panicked, thinking she might tease me for wanting it so soon, and my voice faltered. But when I calmly observed Miyu, I noticed she was fidgeting, her hands between her knees. Maybe her arousal hadn’t fully subsided.

“Tonight, got it.”

Miyu gave a tentative agreement and stood up from the sofa. There were concerns, but the promise was made. Now I had to put everything into tonight.

After all, I’m going to take my little sister’s virginity. I can’t approach it half-heartedly.

“Onii-chan, here.”

Miyu brought a single sheet of paper from the living room shelf and handed it to me.

“Something I wrote when I was still rational.”

It was a small, business-card-sized envelope.

“Should I read it now?”

The envelope wasn’t even sealed, so I could check the contents immediately if I wanted.

“Maybe after tomorrow. Keep it in your wallet so you can read it anytime.”

“Got it.”

When I agreed, Miyu wobbled up the stairs to her room. What could it say? From our conversation, it didn’t seem related to Yamamoto-san. Since she said she wrote it while rational, it’s probably something she couldn’t say when she’s aroused.

But Miyu’s more honest when her rationality evaporates, so this note isn’t a backup for something she couldn’t say—it’s likely meant to reinforce the credibility of words she might blurt out when she’s lost in lust.

Words she can only say when she’s horny, ones she wants me to believe are her true feelings. Given Miyu’s personality, the only thing that comes to mind is a love confession—a super sappy one. But would she really use a letter for that?

No point overthinking it. I’ll rest in my room to prepare for tonight. If I have extra time, I’ll study. This summer break has been full of dates, and I still haven’t finished my homework.

I slipped Miyu’s letter into the bill pocket of my wallet, staring at the pristine white envelope. No, it’s still bugging me. Given its size, it probably contains a message of just a dozen or so characters. What kind of feelings could Miyu have packed into such a short sentence?

Also, “something I wrote when I was rational” was an odd choice of words for Miyu. If I take her statement literally, it could imply that when she gave me the letter, her rationality was already shaky.

(…Does that mean—)

Is Miyu still turned on? If she retreated to her room to calm her arousal, then right now, she might be on her bed, touching herself and writhing in lust.

If so, I want to help her release it. But just imagining her masturbating is exciting, so part of me doesn’t want to stop her. If I went upstairs and listened closely, could I hear her lewd breathing? Or with my heightened senses, maybe I could pick up the rustle of her clothes through the door.

My feet moved toward the stairs unconsciously. I wasn’t planning to eavesdrop. I was just going to my room to study. My focus would only stray for a few minutes.

Click. The sound of a door opening upstairs came just as I steeled myself and stepped onto the stairs. I hurried back to the living room, pretending I hadn’t been thinking about Miyu by busying myself with dishes in the drying rack. Miyu came down the stairs right after leaving her room and returned to the living room as if nothing had happened.

Her expression, though subtle, was faintly flushed with a warm glow. Without sparing me a glance as I stood in the kitchen, Miyu grabbed a magazine and flopped face-down on the sofa. If she had been masturbating as I imagined, it was too quick. Miyu’s body is as quick to climax as mine is to ejaculate, but a masturbation session to calm her arousal shouldn’t have ended in just a few minutes.

Was she not masturbating, or am I overthinking it? Feeling pathetic for my unwanted erection, I lingered in the kitchen, watching Miyu to hide my lower half.

My little sister, sprawled on the family sofa, engrossed in her magazine. During our earlier intimate moments, I was hyper-aware of Miyu as my lover, but seeing her like this, living an ordinary moment, she was unmistakably my sister.

We’ve lived under the same roof forever, faced each other countless times at the dinner table, and known each other since we could barely speak. And tonight, after fifteen years of living together, I’m going to have sex with my real sister. Miyu and I are proper lovers now. We’ve been intimate many times, so having sex with her as my sister doesn’t carry any special weight for me. My sense of boundaries has always been loose, and if anyone’s concerned about it, it’s probably Miyu.

(What does Miyu prefer?)

After confirming my erection had subsided enough not to be noticed, I returned to the sofa where Miyu was. She’s always been the one more hung up on our sibling relationship. Even today, she emphasized being my sister, which makes me wonder if there’s some deeper intent. Is she trying to ingrain in me the reality of our siblinghood, reminding me that it’ll inevitably complicate our lives? Either way, I feel like Miyu wants to be treated as a sister even as my lover.

Even when I sat close, Miyu didn’t acknowledge me, just kept flipping through her magazine. I perched lightly on the empty space, looking down at her back. I wanted to cuddle up and be affectionate with her, sex aside. As lovers, that should be fine.

When I touched her hair, she didn’t react. Running my fingers through it, I could see the pink streaks. It was silky and pleasant to touch. I wanted to hug her and grab her breasts—not as a sexual act, but as affectionate contact.

If I gave up now, I’d be a loser forever. With that resolve, I gently placed both hands on her breasts. Even Miyu couldn’t ignore that, shooting me a silent stare for a moment.

“I thought you were up to something. What’s that about?”

“Well, I wanted to hug you tightly, but I hesitated and ended up like this.”

When I explained, Miyu pondered for a few seconds before responding.

“That’s something we both need to work on, I guess.”

She flipped onto her back, still holding the magazine.

“Meaning?”

Is Miyu also holding back from wanting to cuddle with me?

“You hesitate to be affectionate because of how I used to resist touching you, right? I should’ve been clearer that I want you to touch me more now.”

Miyu spoke seriously, trying to distract from her embarrassment, half-hiding her face with the magazine. I see, I see.

“So I can touch you a lot from now on?”

“Only if you touch me in ways that make me happy.”

“That’s a tall order.”

“I always do that for you, don’t I?”

“Yeah, you’re right.”

Miyu’s touch excites me not just because she’s a beautiful girl, but because her affection is always perfectly tailored to please me as a man. I need to learn from that.

“What happens if I touch you the wrong way?”

“I’ll just say it’s creepy.”

“That’s clear and helpful.”

She’s a prickly sister, but considering she wouldn’t even let other guys touch her, her willingness to let me says a lot about how much she likes me.

“Sometimes I say it’s creepy even when I like it, though. I’ll work on that, so please bear with me.”

Miyu closed her magazine with a snap, clasped her hands, and struck a praying pose.

“I like it when you call me creepy, so it’s fine.”

“You need to fix that.”

“Uh, yes.”

I accidentally let my true feelings slip. Unfortunately, this twisted kink is incurable, and since it’s Miyu’s fault, I feel no guilt.

“Anyway, I’m gonna touch where I want.”

I looked down at Miyu, lying on her back, assessing safe zones. Her neck and thighs are highly sensitive danger zones, her breasts have been touched more than enough, and I wasn’t in the mood to pat her head. That left her arms or stomach. If asked, I’d pick her stomach without hesitation, so I rubbed her abdomen over her clothes.

“How’s that?”

“Hmm… I was surprised you went there, but it’s not bad.”

As I rubbed her stomach, Miyu’s expression softened, as if reassured. Touching her felt good, and seeing her enjoy it warmed my heart.

Is this how people with dogs feel? Miyu stopped reading, closed her eyes, and let me stroke her stomach contentedly. Feeling she was used to it, I slipped my hand under her shirt to touch her bare stomach. She squirmed at first, as if ticklish, but soon relaxed. Her slim waist still had a soft, pinchable texture, making it incredibly pleasant to touch. Her skin was smooth and supple.

So this is Miyu’s stomach. We’ve been intimate many times, but I’ve never touched her like this. I think I sniffed her stomach once—it was thrilling. After all, inside this stomach is her womb, where my semen could fertilize her egg. It’s a sacred part, yet that’s exactly why it excites me.

“Nn… Ah…”

As if reacting to my lust, Miyu let out a sudden moan. She looked flustered, her face reddening.

“S-Sorry.”

Miyu apologized sheepishly. I felt guilty for touching her with impure thoughts, but she probably wanted to keep this affection separate from sex for my sake.

“You okay, Miyu?”

“Y-Yeah. I felt some wicked vibes from you, but it might be my fault this time.”

As expected of my sister—she sensed it intuitively.

“You’re right. My bad.”

I apologized again, but Miyu didn’t press further. Her face stayed flushed. I worried she might be sick, but her lack of resistance strongly suggested it was arousal. As I suspected, when she handed me the letter, she hadn’t fully quenched her desire.

“When you went upstairs, did you… not do it?”

I asked indirectly. Still letting me rub her stomach, Miyu hid her mouth with the magazine and stared at me.

“I thought about it but stopped.”

“Why?”

“That’s a secret. Besides, we’re doing it tonight anyway.”

It seems Miyu went to her room intending to masturbate, maybe touched herself briefly, then stopped for some reason and came back downstairs.

“If you don’t want to say, I won’t pry. But there’s something else I want to ask. Is that okay?”

“Go ahead.”

—I decided to be a bit more honest today.

Miyu added in a barely audible whisper, meeting my eyes.

“I’m torn between loving you as my sister or as a woman. I was leaning toward loving you as a woman, but you seem to want to keep our sibling dynamic.”

“Oh, that.”

Miyu seemed to have anticipated this question.

“I’ve got an answer prepared, sort of.”

Her response started off vague.

“But first, I don’t want you to overthink whether we’re lovers or siblings. Okay?”

“I don’t mind, but I’m curious why. I’ll hear your answer with that in mind.”

I decided to listen to her response first.

“I want to keep thinking of you as my brother, and I want you to cherish me as your sister. But I also want us to be lovers… at least until we’re both adults.”

Miyu wanted to remain my sister. While our romantic relationship was the foundation, she didn’t want to be “a lover who’s also a sister” but rather “a sister who’s also a lover.”

“If that’s the case, I won’t force a lover-like attitude. …That’s fine, but what did you mean by ‘don’t think too deeply’?”

“Well, you know, if I have an answer, there’s a reason behind it. If it didn’t matter, I’d just say ‘whatever you want.’”

“Fair enough.”

For her to wish I’d stay her brother even as lovers, there must be a significant reason. It could even be a crucial one that affects our future.

“See? You’re making that serious face again.”

“Oh, sorry. So, what do you mean?”

“It means I’m about to tell you why I want you to stay my brother.”

So she wants me to listen without overanalyzing.

“Got it. I won’t think too deeply.”

No matter how intriguing or surprisingly simple her answer, I’d accept it as is. Whatever the reason, the fact that I’m Miyu’s lover and brother won’t change.

“I want you to think about this from your own perspective, too.”

“Okay.”

“We’re going to keep having sex, right?”

“Yeah.”

“Like… having sex, you know.”

Miyu tossed the magazine to the floor, took the hand I had on her stomach, and grabbed my other hand, guiding me to kneel between her legs. It was the classic missionary position, the standard stance for sex.

“We’re gonna have sex, right?”

“O-Of course. Specifically, tonight, something like this…”

Yes, this is probably how Miyu and I will have sex tonight.

“This is what I mean, Onii-chan.”

Miyu clamped my sides with her legs and pulled my arms, drawing my hips deeper between her thighs, our private parts nearly touching.

“I-I see. Uh, what’s that about?”

My heart raced as I tried to grasp the true meaning of her words. What’s with this missionary position? I’ve been intimate with Miyu countless times and had sex with other girls, too. So, I thought doing the real thing with Miyu wouldn’t faze me. Or so I believed.

“Onii-chan.”

Still holding my hands, Miyu pressed her elbows together to lift her chest, staring intently at me. Her provocative pose overlapped with the image of her lounging on the sofa, reading a magazine.

We’ve lived together in this house forever. I’ve seen her sprawled on the sofa with a fashion magazine countless times. She’d greet me in the hallway when I got home, call me “Onii-chan” when she needed something, and talk to me.

That’s the person I’ve spent fifteen years with. And now, that same real sister is engaging in this lascivious intimacy with me.

“Miyu…”

A murky emotion I hadn’t felt when having sex with other girls swelled in my chest. It wasn’t unpleasant—accurately, it was the intense thrill known as “taboo.”

I couldn’t help but picture it: me, her brother, taking my real sister’s virginity. Inserting my erect, grotesque male penis—designed to impregnate, usually used only for excretion—into her body. Making my innocent, inexperienced sister accept it was an utterly immoral idea.

“I want to have sex with you as your sister.”

Miyu continued, her expression no longer burdened with serious contemplation. She was just a cheeky girl her age, gazing at me.

“Because it’s more exciting.”

Suppressing maximum embarrassment, Miyu finally voiced those words. That was the first true confession from the Miyu who’d vowed to be as honest as possible. She didn’t want to stay siblings to avoid future obstacles—she wanted me to love her as a sister because having sex with her brother was simply more thrilling.

“Miyu…!”

My groin, unsurprisingly, swelled painfully. Matching that level of arousal, Miyu’s shorts were soaked through.

“Hya… No…!”

“Let’s do it, Miyu. I can’t wait until tonight. Let’s do it here.”

“N-No, um, I want my first time to be on a bed.”

Miyu stopped me from undressing her, looking up with wet eyes.

“Then let’s go to your room.”

If I’m to embrace her as my sister, we should have sex in her room. She’d appreciate that. That’s what I thought, but—

“…I want you to take me in your room.”

Miyu tugged my hand, making her request.

“If there’s a reason, tell me. I think if I’m embracing you as my sister, we should do it in your room.”

No more beating around the bush. I wanted to bare our raw feelings. Miyu seemed to sense that, and from then on, there was no holding back.

“I feel more like I belong to you if you take me in your room.”

It was the opposite of possessiveness—a desire to be dominated.

“You’re okay being treated like a possession?”

“Yeah. During sex, I get in that mood. Being owned by you… and, to be a bit honest, I don’t mind being used for your sexual needs as your sister.”

Each word dripped with regret for speaking it, making her expression all the more sincere.

“When you say ‘don’t mind,’ can I take that as more than just words?”

When I pressed, Miyu gave an embarrassed “ehehe” laugh.

“Interpret it as you see fit.”

It was the naughtiest answer I could’ve hoped for. Her raw sexual desire was clear—she genuinely liked being used for her brother’s pleasure, an undeniably problematic statement. Yet, oddly, it felt natural.

During the time when Miyu only “processed” my semen, grappling with our sibling relationship while trying to accept her unique condition—that was why her responses were so detached. But looking back, she was also enjoying her situation.

Miyu might be an inherently sexual girl. Her instinctual craving for her brother might have masked her true nature. Her overwhelming lust when she loses control is a mix of her natural desire and her condition, but I never considered which was stronger. It’s possible her condition usually forces her to self-reflect, restraining her innate lust.

“I understand your feelings. But I’ll take your first time in your room.”

I lifted the hands she was holding, pinning them above her head against the sofa’s armrest.

“We’ll sleep in my bed and have sex there plenty in the future. At least let the memory of giving your virginity be in your room.”

This house was bought around the time our mother gave birth to us. Every room holds our entire lives. Miyu’s room contains her entire existence as my sister.

“If we do that, I’ll get horny every time I go back to my room… I’m already masturbating more when you’re not around.”

Miyu grumbled, but this naughty sister probably just wanted to confess she’s been using me as masturbation material.

“Miyu.”

I called her name gently, pulling her hand and slowly helping her sit up.

“W-What, Onii-chan?”

Miyu looked at me, unable to hide her excitement.

“I want all of your life.”

That was my unfiltered truth at that moment. Our lust-filled gazes locked, and I felt we shared the exact same emotion. We just wanted to have sex.

“It’s your cute sister’s life, so treasure it.”

Bold yet unadorned, it was enough of a confession for us to face our first time as brother and sister.

We stood up from the sofa, holding hands as lovers for the first time, and closed the living room door.

It was still early afternoon, the summer sun high. Gripping each other’s hands tightly, we hurried up the stairs.