Science Experiment


“Everyone, one table per group—”


It was our first experiment since entering high school. Why did it end up this way? I guess I had this ‘end of the world’ look at this moment.

It’s not that I hated science (chemistry, to be exact).

The actual reason was the grouping for the experiments.

Once the teacher gave the instruction, us students were assigned to six tables, groups of five, as if we were fish being sold at the market.

So what’s the basis of the grouping?

Yes, the student number!





I, as student number 1, Mizuto Irido, sat next to student number 2 Yume Irido. We briefly exchanged looks, and then quickly looked away.

The implication was basically, don’t you dare talk to me.

Well, as stepsiblings, it wouldn’t be natural for us to sit next to each other for fifty minutes and not utter a single word, so it’s possible to talk a little if we’re just carrying out the experiment. Hmph, just don’t get carried away. I’m just going easy on you because we’re in public, I’d have crushed you into dust if that wasn’t the case.

The adaptability of human beings really was very terrifying, given how I could determine this with a single exchange of looks.


“Please take care of me~, Irido-san!” “Thank goodness I’m in the same class as Irido-san~! I’m really bad at the basics of experiments~” “I get that. I’m really grateful to my parents for giving me this surname.”


“Ahaha …….I’m not exactly good at them either. Please don’t get your hopes up.”


To my surprise, the four others including Yume were all girls—it’s nothing, nothing to be scared of. I was already used to being part of the background. Go ahead, don’t worry about me, and get on with your girl talk.

I followed the instructions written on the blackboard and grimly set up the beakers and other equipment. The girls too set up their experiments while chatting with each other.


“Irido-san, your hair is so pretty~. Did you do anything to it?”


“No, nothing in particular…it’s just longer than when I was in middle school.”


“Woah, I’m curious about you in middle school, Irido-san.” “You must have been very popular back then~~” “Yeah! I was so shocked by the Irido fever after we entered high school—!”


“Ah—no—that’s not, really—”


You’ve started acting really weird ever since you talked about middle school, huh, high school rookie?




Yume glared at me for a moment. Did she use telepathy or something?

After the setup was done, they started to chat and experiment at the respective tables.

I quickly went through the steps and proceeded much faster than the others.


“Oh, Irido-kun, you’re so fast!” “That’s the stepbrother for you~” “Didn’t you two get first and second in the entrance exam?” “Eh!? Really!? Aren’t they geniuses!?”

……I had assumed it was an urban legend that Yume and I were ranked first and second in the entrance exam, but let’s not get carried away. It’s not like we’re suffering from rumors or anything.

In fact, the chilling glare next to me relieved me all the more. She seemed rather unhappy that her friends just praised me. Hahaha!


“…… Well, he’s, my, little, step, brother. He should be capable of this much.”


Yume said casually, but with emphasis.

How long was she going to nitpick about this? Stepsiblings are legally strangers. Who cares about who’s the older one here!? You’re the little sister here dammit.


The other members of the group, perhaps imitating my actions, started to go faster. They were being modest, but we’re in a prep school after all, and they’re smart enough to enrol here.

And so, our group finished our experiment a lot faster than the others.

High school students are the kind of people who spend their spare time chatting with each other, just as corporate slaves spend their salaries on social games. As soon as we realized that we had quite a bit of time left, one of the nameless girls (I was sure she has a name, but I couldn’t remember) whispered,


“……To be honest, Irido-san, do you have a boyfriend?”


Yume’s right hand, holding the thermometer, seemed to move faintly.

At the same time, it seemed my right foot moved as well, but thank goodness it was hidden by the table.


“You definitely have one since you’re so cute, right~.” “Yeah yeah. You might not have one now, but surely in middle school—” “With this face of yours, it’ll be a lie to say you don’t have one—”


Ahahaha, laughter bloomed like flowers, but Yume and I weren’t laughing at all.


“I……I, guess?”


Yume gave a smile that looked like it was made out of wax.


“Not now…… but.”


“Now~?” “In other words~?”


Hey, go for it! I’m rooting for you just now! Hold your shame! Tell them you’ve never had a boyfriend!

Yume appeared to have her neck fixed as she tried not to look at me, and answered with the smile of an honor student.


“……Well, I did…back in middle school?”


Kyaaaaa~!! There were excited squeals. Gyaaaa~! And a blood-curdling scream within me.

Th-this woman……!!

It’s rare of her to not lie because she just couldn’t give up the desire to look good…!


“Eh, ehh!? Who is he, how’s he like!? ” “Is he cool!? He’s definitely cool, right!?”


“No, well, he’s just, ordinary…not particularly…cool.”


“So that means you two broke up—Is it because he went to another high school?”


He’s sitting at the same table.


“Say say, is it a little, like, heart throbbing story?”  “Did you kiss!? You kissed, right~!?” “Don’t say that! That’s lewd! Ahaha!”


“Y-yes. O-of course I kissed him, you know? “


Ah, she’s digging a deeper hole here.

She got that look that she’s going to spill the beans.


“Eh?” “Where, where!? In your boyfriend’s room?”


“Erm…,we-well, on the way home, from school?”


“Which way? Which way!?”


“…He asked me if he could…”


—What the hell are you talking about so openly, you idiot!!!!!!!!

You could have just digressed or made up a story…!! Why do you have to tell the truth at such a critical moment…!

I couldn’t take it anymore, so I used my secret technique, fake sleep, to lie prone on the table and cover my ears.

But I could still hear them talking.


“Did you go on a date? Where did you go?”


“H-he and I both liked books, so we went to the library a lot. Talking’s not allowed there, so we would write on the edge of our notebooks……”


“Wow! That’s so cool!” “So, did you two kiss at the library? Tell us?”


“I-I didn’t. It’s…”


“Ah, she’s looking away!” “She clearly did.” “She totally did it~.”


“I-it’s him! He forced me to…!”


“So, how was Christmas? Did you get any presents?” “Oh, I want to hear that!”


“…H-He called me at night and asked me to look outside…”


“And then you saw him!?” “Woah! That’s a surprise!” “That’s something a good-looking guy will do. He’s definitely good looking. “


“No, no, we just met and talked…


“I would have liked to have seen Irido-san’s boyfriend.” “I think he’s definitely cool.” “My handsome chad sensor is blinking. Do you have any pictures~?”


He’s the one pretending to be asleep next to you!



We’re on our way back to the classroom after the session ended.

“……Oy, showoff.”

“……What, fake sleeper?”

“I suddenly have the urge to tell those people about your love story involving that handsome chad. Are you fine with that?”

“Absolutely not……!”


Yume stared at my face intently as she clammed up “uuuuuu……!” and she continued to groaned.



“…………I’m sorry………….!”

“Good that you know. I’ll spare you if you get me a paperback.”


Yume looked down and apologized faintly, and I continued with a much softer voice than before.


“(……But let me correct you on one thing. I didn’t start that incident in the library, it was you—)”




After delivering a low kick to my calf, Yume scampered off to her friends.

……I can’t be the only one getting embarrassed all the time. I’ll repay this debt to you one day!




Inside the little stepbrother’s bookshelf


“…Huh? I didn’t have the previous volume of this series…?”


I tilted my head slightly as I couldn’t find a book I wanted to reread.

Did I have it somewhere else when I moved in? No, I’m pretty sure I packed my books very carefully…

Or maybe I never had it to begin with? No, no, no, I’m pretty sure I read it before, and I remembered I didn’t get it from the library—supposedly?




I felt deflated.

Yes, I borrowed it from him, back when we were dating.

If that’s the case, I’d have to borrow it from him again…the bookstore would be closed by now even if I wanted to buy it.

But how should I tell him?

Do I just ask to borrow it? No, that’s impossible. It’s him after all, he would definitely use this chance to come up with some strange condition.

Otherwise, maybe I should count all the favors he owes me and force him to lend it to me…hm, yes, yes. That’s the best option. Maybe I should be able to use that incident as leverage…


I did my calculations, and left the room.

At this time of day, he should be in his room reading. We’ve been living in the same house for a while now, and I realized he really wouldn’t do anything other than to read.

I arrived before his room, and knocked on the door according to our initial agreement.

What, I waited for this grumpy voice to reply—




There was no reply.

This was—the pattern of a locked room murder, like a mystery novel!

I twisted the knob with some excitement, and it opened normally. Seriously, it wasn’t locked?


The lights were on.

I had a peek inside and saw Mizuto’s back. He was lying prone at his desk.

Huh? Was he really dead? I couldn’t find the murder weapon though.


“… Mizuto-kun?”


I tried to call him discreetly, but he didn’t answer.

I tiptoed into the room, approached the desk Mizuto had fallen upon, and peered at his face..

Mizuto’s eyelids were gently closed and he was breathing regularly.

The paperback book remained in his hands. It seemed that he had dozed off while reading. That’s a rare sight. Did he stay up late last night?

I lifted my drooping hair and brought my mouth close to Mizuto’s ear..





He merely twitched a little even when I called him twice by his ear. He didn’t sleeptalk.

…Though I couldn’t say I was expecting to hear his sleeptalk or something.


It wouldn’t be nice to just wake him up, so let’s wait until later—well, that was the goody goody kid thought process I had for a moment, but on deeper thought, I felt it was the perfect opportunity. I should use this chance to borrow the book I wanted and return it before he wakes up.

So I made up my mind, and went to the bookshelf.


A bookshelf can reflect a person’s heart—or so I heard. By this theory, Mizuto’s bookshelf showed how he was meticulous and not biased towards any genre, given that his books were neatly arranged based on labels and size, ranging from light novels to historical ones. It seemed he hated to lose out too.

I checked the spines of each book and looked for a corner where mystery novels were grouped together.

“This is—light mystery, right. “

First off, I’m not interested in books that don’t have corpses (not dead bodies though).

Despite that, the area next to this section was where the paperback detective novels were at, and I quickly found the book I wanted. Seriously…is this guy challenging me, a full-fledged fundamentalist, by putting light mysteries and mystery novels next to each other?

Well. I’ll spare you this time. I pulled out the book I wanted—




After removing the book, I caught a glimpse of another book’s spine.

So there were two layers to the book shelf? Personally, I would read the same book repeatedly, and I wouldn’t like to do this since it would be inconvenient to take the book out…

I stuck my hand in tentatively and took out the book I saw in the back. Why was the title of the book strangely long…?

I had a look at the cover that contained brightly colored illustrations. A light novel?

I I flipped through the cover almost instinctively, and the first color illustration I saw was—




Bam, I slammed the book shut.


Was I mistaken?

Did I just see illustrations that were inappropriate for my age…?

I-I should be mistaken, right? Of course. It’s a light novel, it’s just a little too revealing.

Terrified, I looked at that illustration again.




Skin tones were spread across the page, and there was lewd-looking sweat, along with a seducing pose. Most importantly, the blushing expression!

…………I-it’s an erotic novel…………

I-I’ve never seen one before…I’ve heard of them, but to think they exist…….




I had the book opened as I looked towards my little stepbrother who remained prone on the table.

O-of course…he reads everything…he did think of doing such a thing with me. It’s natural that he would read such books…

The old me might have been disillusioned, but ahhh, thank goodness there aren’t any illusions left to destroy now. Silver lining. Thank goodness I hate him now—!

Well, I’m going to put it back where it belongs.




I glanced again at my dozing little stepbrother.

……No. No, no, no.

I-It’s not that I don’t want to know what gets him turned on or anything like that.

It’s just a little, well, unusual of him!

I’m just showing legitimate interest in exploring a completely unknown genre, as a self-proclaimed reader…!


“…T-This is just me browsing through…it’s just…it’s just…”

I chanted to myself repeatedly and flipped the page.

Of course, at first glance, it was just a normal novel. I scanned through the pages quickly, not knowing when Mizuto would wake up.


And then I came across a page with an illustration.

It was in monochrome, and wasn’t as impactful as the cover illustration, but it showed a girl dressed indecently in a sensual manner.

But more shocking to me were the paragraphs next to it.




It was just a scene of a girl’s back being massaged, portrayed with more precision and care than most novels. My heart pounded for some reason though. I could basically feel the protagonist’s heart throb.

…Is it even okay to write such novels…?

Well, how should I put it? Since I only read old novels, the shock to me was amplified, especially since I had read terms that used to be censored being depicted so freely.

I flipped through more pages and picked up the text around the illustrations. Wow. Wow. Wow. …….


“‘—What are you doing?’


I was reading the fourth scene when a hand reached out from beside me and snatched the book away.




I looked aside in surprise, and saw Mizuto check the book with a doubtful look.

H-He woke up!? When did he!?


“I had a feeling someone was here…are you finally interested in light novels now? “

“Ah…no…t-that’s, not it…!”


My face was about to explode.

H-he saw…! He saw me…! He saw me peek at an erotic novel…!


“You were reading this? That’s surprising….”


Mizuto said as he flipped through the pages I had read through. Ahhh ……! Ahhhhh ……!

“I-it’s all…your fault!”


My head heated up, and I couldn’t help but shout,


“It’s because you’re hiding that book! T-That’s not something people of our age should buy, right!?”



Mizuto raised his eyebrows lightly and looked down at that lewd illustration.


“Wait, are you talking about this book?”

“Y-yeah! This erotic novel—”

“It’s not an erotic novel. It’s an ordinary romcom light novel.”




How’s that ordinary?


“……Haaaa, I see. That’s what you think since you aren’t used to it, right?”


Mizuto muttered to himself as he looked at me, and seemed to have understood something.


“Wh-what do you mean…? We-we’re talking about a girl’s naked body here—”

“It’s true that some light novels are pretty much erotic, but the content and the illustrations are par for the course for a young boy’s label…it’s true that the fanservice scenes might be really overwhelming though.


Y-you’re kidding, right…? That’s ordinary…? All ages…?

I shivered away, “Hmph” and Mizuto suddenly snorted.


“This much is enough to make you blush.”



My head was filled with embarrassment and frustration, and I was completely flustered.

Uuuuuu……! I want him to eat his words…!!!  I want to make him blush for his vexing mockery!


“…I-I was just shocked.”


I turned my face aside and said spitefully.


“I-I was just a little immature, so I felt embarrassed when reading it! I mean, what is this!? How can a girl possibly make su-such lewd noises from a massage!? This author has absolutely zero experience in lover!”



Mizuto’s eyes narrowed slightly, and there was a glint in his eyes.


“Did you just… attack the author’s personality?”

“Eh? No, that’s…”


While he continued to squint, Mizuto continued to close in on me. I was about to turn away, but he grabbed my wrist before I could.

He pulled my arm and brought his face close to me.

The eyes showed a faint glint as they peered into mine.


“You sure have lots of guts to enter someone’s room while the person’s sleeping, took a book to read, and the biggest of them all, breaking the ultimate taboo of attacking the author’s personality…”

“Ah, eh, no…th-that’s not what I meant…”

“Get onto the bed.”



He said something completely unexpected with a serious tone, and a strange voice came from a strange place.


“Lie face down on the bed. Let’s see if the description in the novel is correct—if a massage can really cause lewd noises.”

“Ehh, ehh, ehh, you’re kidding—kyaaa!?”


I was nudged gently on the shoulder, and fell backwards onto the bed.

With his back facing the light, Mizuto looked down at me.


“Now then, turn around.”

“No, wai—”


Mizuto turned me around as if I was a log.

I struggled tried to get up, but before I could, I felt weight on my thighs. Mizuto sat down, and I couldn’t move.


“Eh, eh, you’re kidding, right? Are we seriously doing this!?”

“It’s nothing to be ashamed of, right? I’m just a kind stepsibling who wants to give you a massage. So—”


Mizuto crouched down as though he was covering e, and whispered with a deeper voice than usual.


“—There’s no way you would make any strange noises, right?”


I felt a tingle run down my spine.

I hadn’t even been touched yet, but I felt ticklish from my butt to my back.

I hugged the pillow in front of me and buried my face in it.

A-at this point, I just had to endure to matter what…!

And then I’ll prove myself to be correct and win…!


“Let’s start.”


Mizuto’s hands pressed just below my shoulder blades.




The fingers that were somewhat thin and nimble for a guy touched the ribs under my armpits, and it was a little ticklish.

But it’s fine. It’s still fine. If it’s just that much…


He slowly exerted more strength, and I felt more pressure on my back.




Woaoaahhh…uh oh…! My back was a little stiff as I had been reading a book while standing up and hunched over…!


“It’s pretty stiff. I guess it’s because you’ve been sitting and not exercising.”


And then he whispered in my ear. That’s cheating!? Do it fair and square. Fair and square!

I felt a strong weight on my back.


“Nnn—kuu, uu…”


The air was squeezed out of my chest. Yes, that’s all. I just exhaled! I didn’t voice out! Safe!

I pressed my mouth against the pillow to ensure that I wouldn’t let out a voice, just in case.


“…That’s my pillow. Are you sure you want to rub your face in it?”




And while I panicked and lifted my face away from the pillow, there was additional weight pressed against me.




I got down on my knees and suppressed my voice from leaking out.

After enduring this wave, my forehead landed on his pillow.


“Fuuu…haaa, haaa…….”

“Didn’t you just let out a voice?”

“I-I didn’t, no…! M-Maybe you’re so unpopular…to the point where you’re hearing hallucinations, aren’t you?”

“Hmm…time to change tactics.”



Mizuto moved his hands.

He went from beneath the shoulder blades to somewhere a little lower—the waist.


“No…wa-wait! That’s…!”

“What about that? You’re probably stiff around here too.”


My sides…!


“Here we go—”

“—Mmm, nnnn~~~~~~~~~~~~~~~!!!!!!”


He had his hands on my waist, and the moment he exerted some strength, I ended up voicing out.

My-my sides are my weakness…! I-If he continues to touch…!


“Fuu…kkuu!! Ngh, ha, auuu!”

“Oy oy, what’s the matter Yume-san? Didn’t you say you wouldn’t make noises just from a massage?”

“I-I didn’t, make any, noise—ugh!? Uuu, nyaa!! Uuuunnnngggghhh…!”


I had no idea if I was hurting, comfortable, or embarrassed, but in any case, all I could do was the cover my face with the pillow and flail my calves.

Mizuto did not ease up, and instead increased the strength. The current-like touch continued to race through my body.


“Haa…no…! P-please, spare me…! I-I’ll…nnn! I’ll…apologize…! Nkkyuu! … I-I’m sorry—”

“No can do.”


And then,


With a way harsher tone, Mizuto exerted more strength.



“First of all, you haven’t admitted defeat yet. How about you raise the white flag? Say, ‘I’m letting out lewd noises because my older stepbrother is giving me a massage’.”


Do-don’t you get carried away………!

I was just getting ticklish. It’s a different voice—


“Now I get the trick. Over here?”



The moment he stroked his fingers up from the lowest rib, I ended up gripping the blanket hard.

Arrrrrghhhh…! It’s no longer, a massage, at all—



“—Mizuto~? Are you still awake?”



At this moment, the voice from outside the room caused Mizuto and I to freeze up.

U-uncle Mineaki…!?

Mizuto’s dad…w-wait a sec!? If he sees us like this—


“T-this is bad—d-dad! Wait a moment!”

“Hm? Well, that’s fine—!”


Mizuto hastily got up from my thighs.

Thi-this is bad bad bad!! If he sees me lying on Mizuto’s bed, our relationship will be in doubt…!


“(Can’t help it. Hide under the blanket!)”



The blanket was suddenly laid out over me, and my vision went dark. I felt as soggy as a second-hand item caught in the rain.

I cupped my knees beneath the blanket, and tried to shrink myself as much as possible.


“—Sorry dad. What’s the matter?”

“Ah, it’s about tomorrow—”


I could hear the conversation between Mizuto and uncle Mineaki.

But my consciousness was focused on the sound ringing inside me.

Dokun dokun dokun dokun dokun—

I felt very nervous, probably because I might be found out here…I suppose this would be the reason for this trepidation, and not that I recalled the voice I made that Mizuto heard…


……It’s Irido-kun’s smell.

It’s to be expected since I’m on his bed, but I was naturally reminded of it.

It’s the same smell as when I was embraced—



The blanket was pulled aside.

I lifted my head in shock, but it wasn’t uncle Mineaki over there; it was Mizuto.





For some reason, we stared wordlessly at each other.

After hearing heartbeats for a little while—Mizuto suddenly looked away.


“…Sorry, I got a little carried away.”


He gingerly noted so as he looked away, and clearly, his ears were red.

I looked up at him, my mouth opened, shut, opened again, shut again—and then, I eked out a voice.


“I-I’m…sorry too…for touching your bookshelf without permission.”

“No, erm, it doesn’t really matter—you wouldn’t handle my books recklessly after all.”


For some reason, Mizuto stammered as he scratched his head.


“……So are you planning to sleep on my bed today?”


He looked aside and said so.


It was then that I realized I was lying on a boy’s bed, and I wanted to get away immediately, but before then, I had an idea.

…What shall I do?

This hesitation didn’t last more than an instant. I stretched my legs out, relaxed myself, let my hair rest and looked upwards towards Mizuto—in an uppity manner.


“—Do you think this is better?”


At that moment,

Mizuto’s eyes widened slightly—and then, his face was flushed red like an apple.




Mission accomplished.

My lips eased slightly, I sat up, and I got off the bed.


“Just joking……you perv.”


I said as I patted him on the shoulder, and he glared aside at me while still blushing.


“D-damn you—!!”

“Ah, yes yes. I’ll be borrowing this book then.”


I gently waved the paperback book I was originally aiming for, and felt a relieving stare from behind as I left the room.

I returned to my room, thud, and closed the door.

And then, I stopped there for a moment.

1, 2, 3, 4—5 seconds.


Zzzzzuuuu, my back slid down the door.




I covered my face with the book I borrowed, and fell onto the floor.

I managed to retaliate successfully, but I couldn’t erase the shameful display I had just shown.

I never made such noises to him back when we were dating~…


“……I’ll definitely find the real ero novels next time……!!”


I secretly swore to myself, and put the book I borrowed on the desk.

How could I possibly read while in this mood!! Let’s get to bed!

I darted onto the bed like a serial murderer victim, and finally, it didn’t need to be said that I had an unbelievable dream.


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