While Taking Care of My Shut-In Little Sister, I Somehow Ended Up Ejaculating Inside a Beautiful Girl - Chapter 1: While going about my usual daily routine, for some reason, I ended up having to take back my underwear

Chapter 1: While going about my usual daily routine, for some reason, I ended up having to take back my underwear.

There’s a phrase called “karma” or “retribution.”

It means that people receive consequences for their actions.

When I was a kid, I followed what adults said without question, but as I grew closer to adulthood, doubts started to creep in.

Is that really true?

If people truly receive consequences for their actions, then every murderer should be dead, and those who do good deeds should never experience pain or misfortune.

For someone like me, maybe it’s only natural to end up unhappy, but still…

“…”

I felt like I was being watched. By God, maybe? Or some kind of fairy-like being?

No, that’s ridiculous. Get a grip. I’m probably just half-asleep.

There’s no way I’d have any reason to think someone’s watching me, and it’s absurd to entertain such paranoid thoughts.

Come to think of it, I once heard about a teaching—or maybe it was a religion—that says God is always watching people, ensuring they receive the consequences they deserve. If you apply that to reality, it makes sense that this “watching” could come from within, or maybe from something close by. From that perspective, you’d be expected to look at yourself objectively and strive to act virtuously.

But here’s what I think: that very perspective might be what we call “God’s perspective.” In other words, the mechanisms in our daily lives that make us reflect on our actions, that guide us toward better behavior—couldn’t those be the true essence of “God”?

God doesn’t have to be something grandiose.

It’s simply something—or someone—that watches over a person, a perspective that stays by their side. That, I think, is what “God” is to each individual.

So, even in the tiny garden of an ordinary house, there could be a God or a fairy—

“…Nah, no way.”

I tore my gaze away from the window I’d been staring at so intently. The morning sun had begun to illuminate the edges of the small garden outside.

There’s no way a God or fairy would be in our little garden. What a pointless, idle thought. Instead of letting myself get carried away by such nonsense, I should just move my feet.

Up the stairs to the second floor. Thanks to the morning sun already peeking through, the house was only dimly lit—no need for lights. The faint, somewhat gloomy brightness was enough to keep me from tripping on the stairs.

I passed my own room and stopped in front of the door to the room at the end of the hall.

I was carrying a tray with breakfast on it.

“Brought you breakfast,” I said, instead of knocking.

I tried to sound casual but not cold, consciously softening my voice.

I didn’t expect a reply.

“Brought you breakfast,” I repeated.

I didn’t knock. I wouldn’t go inside—because the door would never open in front of me.

“…”

No response came from the other side of the door. Not even a sound.

Just silence. Or perhaps, a deliberate hush.

“I’ll leave the food here,” I said, placing the tray on the floor.

The meal was carefully wrapped in plastic, as if I’d known this would happen.

It wasn’t restaurant-quality by any stretch—my cooking skills are modest at best. Still, I’d put thought into the nutrition, balancing a main dish, side dishes, and staples.

This was the result of my efforts and practice. In our house, where both parents are ridiculously busy, you have to manage this much just to get by.

It’s not much, but it’s the best I can do. The person in the room will eventually open the door, take the tray inside, and eat quietly. Once they’re done, the tray will be returned to its spot.

If I’m still upstairs, the meal won’t be touched, so I head downstairs to eat my own breakfast in the living room. I kill time before school by messing around on my phone. It’s the usual routine.

There’s no chance of eating with the person in that room, and I rarely even catch a glimpse of them taking the tray.

“Login bonus time! Be grateful! Someone like you doesn’t even deserve this honor!”

On my phone screen, a haughty 2D anime-style girl with her eyes closed and nose turned up appeared in Live2D animation.

Her long, straight hair was a subtle shade of brownish-black, and despite her high-pitched voice, her appearance was surprisingly refined. When I first saw her, I was mildly surprised—she wasn’t the stereotypical blonde with drill curls. Drawn in by her hair color and style, I set her as my game’s home screen character.

…But, honestly, her personality is starting to feel like a mismatch for me, so I’m thinking of switching to another character soon.

That kind of thinking would make me a total jerk if applied to a real person, but thankfully, this is just a game.

I started browsing through my roster of characters, double-tapping or long-pressing to check their details and voices, picking out a new one.

You can only display one character on the home screen at a time, but you can select up to three, swiping to switch between them instantly. It’s like some kind of digital harem, but these characters patiently stand by without complaint—a testament to their protagonist-level endurance. I don’t pay them with my hard-earned part-time job money, but I figure I’ll keep playing the game for a bit longer.

By the way, I’ve maxed out the affection levels for about ninety percent of my female characters. It’s almost too easy—hand over some gifts, and they’re head over heels for you. What a casual game. Real life, on the other hand, feels like a brutal grind.

Oh, and this game is a port of an R18 PC browser game. After maxing out affection with gifts, you can, ahem, enjoy certain honors. Lucky me.

…That said, despite poking fun at the gift system, I can imagine it’s a simplified version of building a relationship—going on dates, getting closer, and exchanging meaningful gifts, like a ring during a proposal. That’s the idea, at least.

But no matter how much I can rationalize it, I’ve never used this game for that kind of purpose.

Part of it is because I’m hooked on the game’s battle mechanics, but more than that, I just… can’t.

Even pink, skin-heavy games feel gray and lifeless to me now.

Even during my hobbies—my escape from reality—thoughts of the real world creep in and leave me deflated. I’m only a first-year in high school; I shouldn’t be this burned out already. I can’t let myself believe I am.

If I just wanted to get off, watching adult videos would be quicker, but even then, I’d feel hollow afterward. Lately, even getting it up has been a struggle—wait, am I… am I getting ED? Erectile dysfunction? Impotence?

…Maybe I am.

The deeper I spiral into these thoughts, the more dangerous they feel—an indescribable sense of dread and urgency. I know there’s no clear solution, and I know panicking is pointless, but still…

“Yawn…”

I interrupted my endless train of thought with a yawn, just as my phone chimed with a notification.

A pop-up at the top of the screen alerted me to a new message.

“Morning! Sleep well last night?”

I opened the messaging app. I keep my phone on silent at night, so it doesn’t buzz or ring. I’m supposed to check for messages in the morning, but lately, I’ve been deliberately avoiding it.

And the reason for that is—

“Ugh…”

In the list of message threads, one name stood out with a glaring [99+] next to it. Maxed out.

Back when I played puzzle games, seeing “99+” next to a monster’s stats felt like a badge of pride. Now, it just makes me dizzy. Naturally, the sender of the new message and this maxed-out thread are the same person.

“Urgh…”

I swiped through the messages, scrolling back.

The one before the latest was from last night—probably late, maybe midnight? From there, the messages came in at a relentless pace, sometimes with barely a minute between them.

It’s like she spent an entire hour, non-stop, sending messages… That’s kind of terrifying.

“You asleep?”

The thread ended once they were convinced I was asleep, but it took way too long to get there.

Scrolling further back, it was clear she was desperate to talk.

“Hey!”

“You asleep?”

“Did you fall asleep?”

“Yo!”

“Yo!”

Every now and then, she’d throw in cute stickers or emojis to play up her girly charm, but her overwhelming need to talk was impossible to ignore. It was a bit much.

“Was she seriously like this the whole time?”

I voiced the obvious question, scrolling further back.

The start of this whole frenzy was…

“Yahho! Can we talk tonight?”

But before that hour-long barrage of messages, there was a message from around 9 PM last night.

I didn’t reply at all, so as the night went on with no response, she seemed to spiral into this frenzy.

I genuinely feel bad about that. Seeing her more rational messages made me feel a pang of guilt.

“You busy? Wanna talk later? Hit me up when you’re free! ♡”

Up to that point, it was… normal. She was holding back, being considerate.

But a few hours later, around midnight, the tone shifted.

“Hellooo? No good for tonight? Were you busy?”

“If you can’t talk, just say so.”

At first, she was still trying to be understanding, but as time went on, her frustration started spilling out.

“What’s with the read-but-no-reply? Can I ask?”

“Why’re you ignoring me?”

“Or were you just busy?”

“Hey, you’re reading this, right? You’re seeing it?”

“What, you’re actually ignoring me?”

“If I’m being annoying, just say so. I’ll wait till tomorrow.”

“Heeey!”

“Phone battery dead? You okay?”

“If texting’s a hassle, let’s just call!”

“Hey?”

“I wanna hear your voice.”

“I really wanna hear your voice! ♡”

“Oh, you’re asleep, huh?”

“Morning work for you?”

And so on—endless messages with the same vibe, over and over.

At some point, she got carried away and started throwing in suggestive messages like, “Is this some kind of ignore-play? ♡”—written in that creepy “old man texting style.” Then, as if snapping out of it, the messages turned sadder, more sporadic, and harder to read.

I couldn’t bring myself to read through the dozens of messages like that, so I quietly closed the app.

Lifting my eyes from the familiar grid of app icons, I glanced at the analog clock on the wall. It was exactly 8:30 AM.

“Probably done eating by now?”

I climbed the stairs carefully, avoiding creaks, and glanced toward the closed door at the end of the hall.

The tray was… gone.

So they’re still eating. No sign of the door opening anytime soon.

“Another late day, huh?”

I’d have to check if the person in the room plans to go to school or if they need me to pick up anything today—maybe they’ll slip a note under the door. Either way, there’s no chance of me making it to school on time.

I know wanting to see their face or talk to them is a luxury, but… how long has it been since I last saw them?

When they’re so thorough about not making a sound, it’s like their very existence has sunk into the distant sea of memory, beyond the horizon.

But that’s not true. They’re like an unsetting sun. Their smile was like the sun itself—a person whose very presence is like sunlight to me. I could never forget that, no matter what.

“It’s already this late?”

The living room clock read 8:45. I must’ve zoned out for a while.

Even though I couldn’t see it from the living room, my eyes drifted toward the closed room upstairs.

“Late again today, huh?”

Muttering with certainty, I acknowledged another unchanged day in our routine.

The person who once stole my gaze is, as expected, holed up again today.

My little sister is a shut-in.

T/N: I deliberately used They/Them for the mysterious effect as her gender was never mentioned, not even the way MC referred to her.

*

“All done.”

I brought in the laundry that had been drying overnight in the garden, called the school to report my late arrival, and finished my pre-school errands. After a quick check in the hallway mirror, I locked the front door and stepped outside.

That’s when I felt someone behind me.

Startled, I whipped around.

“Yahho! ♥”

A girl raised her hand lightly, beaming with a delighted smile, standing there cutely.

“Morning.”

“Morning! ♥”

Her name is Onodera Yuu.

She’s what you’d call a childhood friend, a neighbor, or maybe a lifelong connection.

With her big, expressive eyes, long lashes, well-defined nose, cherry-pink lips, and glossy hair, her appearance is flawless—a beauty polished to perfection. Yet she never lets it go to her head, always treating everyone kindly. She’s a top student, excels at sports, and is undeniably talented.

From what I recall, she’s always been popular, but since starting high school, she’s been officially crowned a campus beauty and has already received confessions from several people.

“Hey, Ren-chan, something’s different about me today. Can you guess what?”

Yuu tilted her head down slightly, looking up at me with those big eyes. Given our height difference, she’d have to look up anyway, but she was doing it on purpose, pairing it with a cheesy line straight out of a new-couple playbook.

“Something different, huh?”

I scanned her for changes. Her dark brown hair was its natural color, styled as usual in a single braid draped over her left shoulder. No new accessories, no tweaks to her uniform—she was the picture of “prim and proper,” the textbook “model student,” as always.

So, maybe… her body?

“…”

“Oh! ♥ Where’d you just look?”

“Your face.”

“Correction. Where did you think was different? ♥”

Even though I hadn’t shifted my gaze, Yuu somehow read my mind.

Right—her chest.

I couldn’t help but think her chest had… grown.

It’s not like she’s got a huge bust, but it’s not small either.

Yuu’s chest is in perfect harmony with the rest of her body—a miraculous balance.

To put it bluntly, it’s average. To be honest, it’s ideal. Personally, I find this size way more appealing than either flat or oversized. But if it’s been getting bigger day by day, part of me wants to see where it ends up, while another part feels a little wistful…

…No, hold on, calm down. That’s not an appropriate answer.

I shook off the impure thoughts racing through my head.

“Guess you can’t figure it out, huh?”

“Wait, I didn’t say I couldn’t figure it out.”

“Right, right! So, what’s different? ♥”

Yuu kept looking up at me from point-blank range, her eyes sparkling with expectation. It felt like she was demanding I trust my instincts. Resigned, I gave her the correct answer.

“New perfume?”

“Correct! ♥”

Relieved by Yuu’s… sloppy grin—no, her satisfied expression—I let out a sigh. It’s been a while since we started this morning greeting routine of exchanging hellos by the front door, but every now and then, she throws in these little quiz-like challenges. She seems to do it just for fun, but for me, it’s a jolt of weird tension that snaps me awake first thing in the morning. Not that I’m complaining—it does sharpen my mood, so I’m kind of grateful. Could it be that I’ve been sleeping better at night lately because of Yuu?

“What do you think of this scent?”

Yuu rolled up her uniform sleeve just a few centimeters and held her wrist up to my nose. A soft, clean fragrance, like soap, wafted gently toward me. Her previous floral scent was nice, but I think this one’s good too.

“Pretty nice, isn’t it? I might like it better than the last one.”

“Really? Then maybe I’ll stick with this one for a while! ♥”

Yuu, all bubbly and animated, put a hand to her cheek, looking a bit embarrassed.

Watching her, I couldn’t help but think: she’s seriously the healing factor in my daily life. Her very existence feels like a reward.

“You’re such a perv, Ren-chan! ♥”

“Hey, I just answered your question, didn’t I?”

Yuu shot me a teasing side-glance with a smile, and I hurriedly reined in the weird switch that was about to flip on in my brain before starting to walk. Yuu fell into step beside me, and just like that, we were heading to school together.

…But thinking about it, school’s probably already started by now.

I couldn’t help but have some thoughts about our leisurely pace, so I turned to Yuu.

“By the way, it’s getting pretty late, isn’t it? We’re totally late for school, and you’re just strolling along like it’s no big deal?”

“What’re you talking about now? You’re the one who’s late and saying that? You’re the most laid-back one here, Ren-chan.”

“I’m panicking on the inside, you know.”

I tried to warn her out of kindness, but she shut me down effortlessly.

“You don’t have to go out of your way to match my pace, you know.”

“But we’ve gotta go to school together!”

“That rule—do you really have to stick to it that strictly?”

“Absolutely!”

“Okay, but… really?”

I respect Yuu’s firm resolve—or her dedication to this rule—but when it causes real problems, like today, that’s another story.

I mean, is it really necessary to be so committed to this fake-boyfriend-girlfriend setup?

“Even if it’s just pretend, you’re my boyfriend, Ren-chan. I need you to get that.”

“I get it, I get it. I’m just saying, do we have to take it that seriously?”

“We do have to take it seriously.”

Yuu raised her index finger, emphasizing her point with a “Got it?”

“When a guy and a girl show up late to school together, what do people usually think?”

“Well… if they’re arriving together, either one of them matched the other’s timing, or they both had some reason for being late together, right?”

That’s how I’d think if it involved someone I was interested in—especially if it was my boyfriend. Unfortunately, I can’t come up with too many other scenarios, but those seem reasonable enough.

“Exactly.”

“Oh, got it.”

Looks like I nailed it, and that was exactly what Yuu was aiming for.

“Guys confessing to me was getting exhausting… Lunch breaks, after school—it eats up so much time. Turning them down harshly feels risky, and ignoring them just causes trouble later.”

“Huh.”

It sounds like a luxurious problem to have, but I guess popular people have their own struggles.

“So! We’re gonna subtly flaunt our lovey-dovey vibe to everyone and nip those confessions in the bud!”

“Makes sense.”

What’s honestly surprising is that, even though I’m playing the role of her fake boyfriend, there are still guys confessing to Yuu despite her “taken” status.

The number of confessions has dropped significantly, she says, but a few guys—either unaware of her situation or pretending not to know—have still approached her. That’s why Yuu’s doubled down on her mission to completely eliminate confessions.

Well, that was the whole point of our fake-couple plan to begin with.

“Let’s go all out showing off our lovey-dovey vibes from now on, okay?”

“You’ve got it rough, huh?”

“Don’t act like it’s someone else’s problem. Are you embarrassed? ♥”

“I’m only playing your boyfriend because it’s convenient for you, you know.”

“…”

It is someone else’s problem, fundamentally. Since Yuu and I aren’t a real couple, I can’t help but feel a bit empty when I snap back to reality. I wish she’d consider how that feels for me.

“…”

“Hm?”

Yuu suddenly stopped walking, so I stopped too and turned to look at her.

Did I do something to upset her?

“…”

“What’s up?”

I asked, but I quickly realized Yuu’s blank, unreadable expression wasn’t directed at me.

“Who…?”

“Huh?”

Yuu’s suspicious, barely audible mutter made me follow her gaze back toward the direction we were heading.

At first glance… it was just the same scenery as before. Hedges, front doors of houses, walls—all lining a narrow street where cars could barely pass, stretching out to a dead end a little ways ahead.

Whether it’s making a scene or ducking into a house, I started thinking about what to do if we ran into someone suspicious. I was about to turn back to Yuu and say, “Maybe it’s just your imagination?”—but then a figure at the edge of my vision made me snap my head back.

“Whoops, got caught.”

Emerging from behind a telephone pole was a girl with golden-dyed hair tied up in a two-side-up style.

Wearing the same high school uniform as us, she flashed a sly, almost sleazy grin in our direction.

“You two are super late today, huh? Pretty steamy, both of you.”

She’d probably been hiding behind the pole, waiting for us to get closer. Total creep behavior. If Yuu hadn’t noticed, she might’ve jumped out and yelled to scare us as we passed by.

“Morning, you two~”

“Morning, Tsuki-chan.”

“If it isn’t Miss Usotsuki herself.”

“Ren-kun, seriously, stop with that nickname already.”

Her real name is Tsukimi Yakko.

She looks like your average cute girl, but in reality… well, she’s got a bit—no, a lot—of a lying streak. (Therefore Usotsuki-chan, meaning Fibber-chan or a liar.)

“Running into each other at this hour? What a coincidence.”

“Coincidence…?”

“Yeah, total coincidence.”

I held back Yuu, who was giving off a tense vibe, and played along with Usotsuki-chan’s comment.

“Ren-chan…?”

I could feel Yuu’s suspicious gaze on me as I observed Usotsuki-chan.

As usual, Usotsuki-chan was grinning slyly.

Yuu often flashes a goofy smile herself, but Usotsuki-chan’s grin feels… different. Alien, almost.

It’s hard to pin down, but if I had to describe it—it’s like there’s something hidden behind her narrowed eyes, something she’d never show us.

I couldn’t figure out why she’d go so far as to risk being late herself just to ambush us like this.

But before I could ask, Usotsuki-chan spoke up first.

“Both of you late on a Monday morning? How naughty! ♡ What were you two up to last night?”

“I was sleeping.”

“Alone?”

“? Yeah, obviously alone…”

I could’ve sworn something glinted in the depths of Usotsuki-chan’s eyes.

“Oh, right. I saw your message this morning. Sorry I couldn’t reply last night.”

“Hmm?”

When I apologized preemptively, Usotsuki-chan seemed impressed by my sincerity. She took a step closer, leaning toward my chest.

She gave a little sniff, then looked up at me with another sly grin.

“Kyahah! ☆”

“…”

While I was still figuring out how to react, Usotsuki-chan turned her smirking face toward Yuu.

“Alright, I’ll forgive you! ☆”

With that, she dropped the grin, went deadpan, and started walking beside me.

Her blonde, two-side-up hair bounced lightly, the tips brushing her shoulders.

Her profile looked almost… dignified. It was a slight shift from her usual demeanor, which made it stand out.

…When she’s like this, she seems normal.

With her sharp, confident eyes, Usotsuki-chan is undeniably a beautiful girl. If it weren’t for her bizarre personality—her habit of lying about trivial things, her knack for telling unfunny lies—she could’ve been genuinely popular.

“Hey. Staring at another girl when you’ve got a girlfriend? What’s that about?”

“Huh?”

I turned to Yuu’s voice from my other side and saw her cheeks puffed out, glaring at me.

“Oh, my bad…”

A guy walking with a beautiful girl on each side might look like he’s got it made.

But in reality, there’s no sweet, dreamy vibe here.

“Hey, Tsuki-chan, what’s your deal?”

“My deal? What do you mean?”

“I mean—!”

Yuu seemed flustered, and Usotsuki-chan narrowed her eyes, clearly enjoying it.

“Oh, right! Ren-kun, check this out!”

“Hey, Tsuki-chan—!”

Ignoring Yuu’s agitation, Usotsuki-chan pulled her phone from her school bag’s pocket, opened an app with a few quick taps, and shoved the screen in my face.

It was a flea market app—where anyone can be a seller or buyer.

And the page she showed me was for… a certain item.

“What’s this… underwear?”

“Yup! ☆”

The screen displayed a pair of men’s underwear.

Alongside the image was an overly enthusiastic product description, and in the notes section, a glaring “[Used]” label.

A bad feeling crept up on me.

“…And why are you showing me this?”

“Look familiar?”

“What…?”

The underwear was a pair of trunks. I switch between boxers and trunks regularly, but lately, I’ve definitely been wearing trunks.

The loose hem, the casual silhouette, the navy base with a red logo, and the elegant white pattern—it looked exactly like the pair I bought last month.

No, it was the same model.

I checked the seller’s name: the ID read “[Tsukimiya©].”

“What… huh…?”

No way it could be that, I told myself, but I couldn’t process the situation. I desperately wanted to know why Usotsuki-chan was showing me this.

Hold on, stay calm. I don’t write my name on my underwear, so there’s no proof it’s mine.

But there’s no name on these used underwear either—which means it could be mine, or it might not be.

Unable to rule out either possibility, I tore my eyes away from the hyped-up product description and looked at Usotsuki-chan with a pleading gaze.

“S-so, uh…?”

The sly grin was gone from Usotsuki-chan’s face.

Instead, she fidgeted, looking almost… shy.

“…I was just gonna show you the listing preview to mess with you…”

After a long pause, she dropped a bombshell.

“But I already listed it! ♡”

“WHAT?!?!”

I felt dizzy, but Yuu’s shocked, horrified yell rang out beside me.

“Gimme that!!”

“Eek…”

Yuu snatched the phone from Usotsuki-chan’s hand and frantically tapped at the screen to check the situation.

“It’s… it’s actually listed… and it’s an auction…”

Yuu’s words, dripping with genuine disgust, hit me hard.

An auction? Never heard of it.

My confused brain was half-grasping the situation while still clinging to the hope that it was someone else’s underwear.

I ignored the fact that the starting bid of one yen for used men’s underwear was climbing toward retail price.

Why is this happening?

The people bidding it up have to be joking—there’s no other explanation.

I don’t even know anymore. Maybe I’ll skip school today.

Yuu, trembling, looked at me.

“N High School… Freshly Worn by Male Student REN… That’s you, right, Ren-chan…?”

“Who knows?”

Don’t ask me. No, it’s obvious. At this point, “REN” is undeniably me.

As the true owner of the underwear, I felt the blood drain from my face, just like it did from Yuu’s as she read the listing aloud.

“Tsuki-chan, just to confirm, the seller is…”

“Me, obviously.”

“Delete it! Delete it right now!!”

Yuu, angrier than I’d ever seen her, got in Usotsuki-chan’s face.

Right, canceling the listing… Yeah, if I think about it calmly, there’s got to be a way to cancel it, right? That’s the fastest way to stop the auction, and even if it’s bid on, canceling means my underwear won’t go anywhere.

“Well… I can’t cancel it…”

“WHAT?!?”

Yuu fiddled with the phone again, then seemed to notice something critical.

“Hurry! Log in and cancel it! You’re the seller!!”

“Uh, well… don’t get mad, but…”

A sinking feeling spread through my chest.

“I forgot the password…”

“…”

For a moment, it felt like every emotion drained out of me.

Yuu must’ve felt the same, staring blankly at Usotsuki-chan without blinking.

“…Teehee! ☆”

Usotsuki-chan winked, stuck out her tongue, and tapped her head in a cutesy pose.

It was the first time in my life that a beautiful girl’s “teehee” made me this furious.