My Stepsister Is My Ex-Girlfriend Volume 1 Chapter 1

The Ex-Couple Refuse to Call – "That's exactly what I hate about you."

I was standing at the entranceway of my house playing out a staring contest like a hoodlum.

My opponent was a girl of the same age as me. There was nothing more or nothing less between us—or so I wanted to say, but there was actually something between us, or perhaps I should say used to be.

"…………Where do you think you are going, Mizuto."

"…………I should be asking you that, where are you going, Yume."

The girl spoke, then me, followed by silence.

That was now the third time.

In fact, I already knew where this girl was heading to without even the need to ask. Her destination was the large bookshop in front of the station. Today was the day when a certain mystery novel publisher released their new books. I was off to get one of the new series from that same publisher and it appears that this girl had the same idea.

That was why we were probably going to end up going through this entranceway together, walk side-by-side to the bookshop, head towards the same corner of it, and line up before the register in succession.

That way, wouldn't it totally look like we're a couple sharing the same interest in fiction.

And that was precisely what either of us wanted to prevent absolutely.

In conclusion, we were stuck in a deadlock.

The timing of that either of us leave the house must be different, but as for the problem of which of us is leaving first—And in order to decide that, here we are now trading diversionary tactics.

The problem would be solved if we talked this out, you say?

No way is that happening. There was no a single thing in the world which could be solved through conversation with this girl.

"—Hmm? Yume and Mizuto? What are you guys doing there?"

Ms. Yuni came over from the living room dressed in a suit.

She was none other than the person who became my mother just one week ago.

In other words, she was the partner of my father's remarriage, and—the actual mother of this girl before me.

"Aren't the two of you going out?"

"I'm just about to go."

'Excuse me', or so I was going to transition into smoothly so as to use this opportunity to make the first move, but Ms. Yuni interjected before I could.

"Oh, could you be heading for the bookshop at the front of the station? I've heard that you are also a book-lover! In that case, I guess you're headed the same way as Yume then? After all, all this girl goes is to either the bookshop or the library whenever she says she's going out."

"……Erm."

"Come on, Mom……"

"Ah! Could it be that the two of you are going together! I'm so glad, Mizuto! You sure are getting along well with Yume! Please continue to take care of her. Yume's kinda shy after all,"

"……S-sure……"

Being told as much, there was nothing I could do but nod in reply.

While at the same time, I could feel a gaze of death right next to me.

"Well now, I'm leaving first. Have a safe trip, the two of you! Be sure to play nice as siblings, okay!"

With that, Ms. Yume disappeared beyond the entrance.

Leaving behind me and her—us siblings.

Indeed, we were brothers and sisters.

That is, by law.

As fellow stepchildren—.

"……Why did you have to nod."

"……It's not like I have a choice, with the flow she going at."

"Why is it that I have to get along with someone like you?"

"Who cares. You think I want to get along with you."

"That's the kind of pa.s.sivity that I hate about you, d.a.m.n otaku."

"And that's the kind of self-centeredness I hate about you, d.a.m.n nerd."

However, our parents never knew.

Only she and I knew the real relations.h.i.+p between the two of us.

That I, Irido Mizuto—

and her, Irido Yume—

—had been dating each other until about a mere two weeks ago.

⯁

In hindsight, with what could only be described as a youthful indiscretion, I had something which you could call a girlfriend from the second to the third year of middle school.

If you were to ask me what was our first meeting like, I could only think of that moment near the end of July, just as we entered the summer break. It was during early afternoon in the library—she was standing atop the stepping stool, reaching her hand out towards the topmost row on the bookshelf.

As it was such a clichéd situation, I'm sure you could already imagine what followed, but I'll narrate nonetheless. I had then took that book for her in her stead.

If I could go back in time, I would've told my past self to just leave that girl alone.

Yet, the me unknowing of the future then caught a glance of the t.i.tle of the book I retrieved, and ignorantly spoke to her.

—You like mystery novels?

I wasn't specifically a fan of mystery novels or what, if anything, I was in the faction that read any and everything—be it pure literature, romance novels or light novels, I read them all without reserve. That was why I knew the t.i.tle of that cla.s.sic mystery novel.

Even though I knew of it, I wasn't particularly a fan of it.

Regardless, perhaps you could call this the disposition of a bookworm, I unconsciously grew excited seeing someone else pick up a book that I had read before. It was something akin to bull getting agitated upon seeing a red cloth, or some kind of unrestrainable instinct, and probably a trap by G.o.d, I thought.

A trap set up by G.o.d.

In other words, it was fate.

Through that fated meeting, the two of us found kindred spirits in each other in what was like a rendezvous in the library during the holiday where there was practically no one else around. And by end of the summer break in late August, I received a confession from her.

And in this process.

For the first time in my life, I gained something which you could call a girlfriend.

And her name was Ayai Yume.

That is, at the time at least.

Coming back to now. ……Without the need for me to spell it out, that was the preface to collapse.

In fact, the chances of a love confession by middle schoolers which did not end up as such were probably around five percent or lower—in reality, you don't ever see any middle school couples who went on to spend the rest of their lives together.

However, to the two of us then, it had seem that we would be the one.

As both Ayai and I were the type who doesn't stand out much in school, our relations.h.i.+p proceeded in a uneventful manner. We would act unrelated before others, while rendezvousing in a corner of the school library, or the bookstores with cafes or public library on weekends, sharing in our interest as our love blossomed.

Of course, we also did stuff that normal couples did.

Ayai basically did not spoke to anyone in her cla.s.s, having stranger anxiety. This caused her to appear mature so to speak in a positive light, or gloomy if a negative light. Thus, we may have progress slower than most, but still we went on dates, held hands, and kissed each other awkwardly—there was nothing particularly of note about us; we just followed the natural progression of any other lovers.

Our first kiss was on the splitting of paths back home from school bathed in the setting sun. I could still remember Ayai's smile with slightly flushed cheeks after our kiss, which was more of a graze of our lips than a touch, as clear as a picture in my mind.

And the current me only has s single response to that snapshot.

Drop dead.

Be it that girl, or the me of that time.

……In any case, that was how we were steadily moving along our relations.h.i.+p, when the turning point slowly approached around the time we promoted to the third year of middle school.

The trigger was the improvement of Ayai's stranger anxiety.

In the course of her relations.h.i.+p with me, her communication skills also improved—and she made numerous friends in her new cla.s.s. Her progress was remarkable; no longer would she be without a partner during physical education, a common sight in her second year.

She herself was also tremendously happy about this improvement, and so did I as I congratulated her on the surface.

That's right, only on the surface.

Then, what of on the inside—that would ended up as my regret. Even as I praised her for her growth, the feelings of wanting to hog her all for myself spreaded within me unconsciously.

The only one who knew of her cute points, her cheerful side, and her smile should have been me only—and so on.

But, that was wrong.

And I indirectly imbued my words with such feelings, causing Ayai to feel troubled as she tried to appease me without even knowing why. But that only got on my nerves even further.

Indeed—I had known. The underlying factor may have been the change in Ayai due to her growth, but the direct reason was because of my trivial desire to monopolize her. She had not done anything wrong. The one who was wrong in the first case was me, I admit it.

However.

Notwithstanding that.

Let me raise a defense for myself. I had then realized my own foolishness at that time, and even apologized to her formally. I had become jealous due to such and such, and I'm sorry for taking it out on you. I'll make it up to you, so please give me another chance—and so and so.

And then.

What do think that girl said?

—So you dislike me getting close to other people, but it's okay for you to get close to other girls?

Huh?

Who could blame me for replying with that.

According to her, I had cheated on her with another girl in the school library where we first met—that was news to me. I told her she probably misunderstood when I was speaking to some member of the library committee or something, but she kept insisting that that was cheating and wouldn't listen to me at all.

In the end, I had to apologize one-sidedly.

Why the heck.

I admit that I was at fault for being too clingy. That's why I apologized and lowered my head. It was up to her to decide if she wanted to forgive me. That I understood.

But why should I have to be admonished for what was a baseless misunderstanding on her part?

Okay, just hold up a moment, I know there's times when the words exchanged get heated up due to impulsive feelings. After all, that's what I did, so I apologized for it. And in that case, shouldn't you do the same too? How can it be that I'm the only one to have to apologize for something unreasonable, while you don't feel the slightest bit sorry? That's just wrong.

—And with those feelings, we patched up on the surface and continued dating for a few months after that.

However—there was absolutely no way to repair two gears which no longer mashes with one another.

What had appeared to be appealing in the past was now a cause for irritation. We devolved to using sarcastic tones with each other, and it even became a pain to reply to each other's message on the phone. The lack of reply further angered the other party and the gulf between us deepened.

We continued like this all the way to graduation only because we were both cowards. It was solely due to the lack of courage on both sides.

We were merely clinging on to the memories of happiness of the past.

Even so, at the point where there wasn't even a single message or word exchanged on Valentine's Day, the future was fixed—there was no further point to this. The two of us understood that implicitly.

I was the one to raise it, with graduation as the opportunity.

—Let's break up.

—Yeah.

It was over just like that. Not a single drop of tears flowed. She did not even appear angry, rather looking like she had been waiting all this time. I thought that I probably looked the same.

She was the girl which I had liked so much…… and treasured some much then.

But now, she was nothing but an irreconcilable enemy to me, akin to what a viper is to a mongoose.

……I must say, love is but a momentary misleading of the mind. I have finally freed myself from this beguilement—

And with the feelings of letting off a heavy load, I graduated from middle school feeling light-hearted.

Then came that night.

My father broached the topic this way with a serious expression.

—Mizuto, your father is thinking of getting remarried.

Whoops.

It seems that the beings known as humans do not stop fretting even at this age. I did pity Dad for raising a child by himself and did not particularly have any objections. I'd very much welcome a remarriage. Just proceed as you please? Not to mention, I had just completed the compulsory education.

I was feeling great. Which was why I had open-mindedly let slide what Dad said next.

—The other party also has a daughter…… Do you not mind?

Come on now, you're telling me I'm gonna get a stepsister at this age? It's as if I'm the protagonist of some light novel. Hahaha!

In fact, that made me even more excited. Now that I thought back, I had probably lost my cool then. That's why, when the lady who was to be my stepmother came to visit with her daughter the next day, it felt like I just got a bucket of ice-cold water dumped over my head.

The one standing over there was Ayai Yume.

Corrections.

By that time, she had turned into Irido Yume.

The two of us staring at each other with our mouths wide open were surely shouting this same words on the inside.

—d.a.m.n you, G.o.d!!

And so, my ex-girlfriend became my stepsister.

⯁

"……Thanks for the meal."

Ayai—or rather, Yume spoke curtly and stacked the tablewares. She then proceeded to the kitchen.

……d.a.m.n it. What bad timing. I had also just finished my meal. It would be weird of me to just sit down here.

"Thanks for the meal."

I also stacked my tablewares and brought them towards the kitchen—where Yume was was.h.i.+ng her dishes.

Her annoyingly long jet-black hair was combed neatly.

She shot a glance at me but did not said a thing. She just continued cleaning wordlessly.

I stood next to her and washed my dishes silently as well.

If possible, I would not have wanted to line up next to her like that as well, but it would be a problem to avoid each other suspiciously. After all—

"Looks like I've been worried over nothing for a boy and girl of this age to become siblings all of a sudden. Fortunately, it seems like they have getting along just fine."

"Indeed! I even saw Mizuto and Yume going to the bookstore together today too. I guess having a common interest sure helps them to bond!"

"That had been my greatest worry these past few days, but it seems I can breathe easy for now."

Dad and Yume's mother were having a joyous conversation in the living room.

The currently remarried couple seemed to living in happiness everyday—completely opposite to us children.

"……You understand, right?"

"……About what."

Yume spoke in a low voice that seemed to be drowned by the flowing water next to me.

"Don't ever make the two of them feel any regrets."

"I know that. I was always planning to take the matter about us to the grave."

"That's fine then."

"……You're so obnoxious in every way. Since when did you become like this."

"If I was any different from the past, then it's 100 percent your fault."

"What?"

"What's wrong about that."

"Hey! What are you guys talking about?"

Dad called out from the living room, and we instantly masked our feelings.

"Oh, nothing much, we're just talking about the novel we bought today, you know."

"Right, we were just discussing about that novel."

"—Ouch."

Yume replied to Dad in a bright voice, while giving me a low-kick where she could not be seen.

"(There's no need to add that, 'you know'. Is your language even okay?)"

"(No need for you to worry about that. You should know that my language in the top 100 placing nationwide.)"

"(……Grr. I can't believe myself for even saying that was amazing.)"

"(I should feel indignant. To think I was actually happy to hear that then.)"

On the surface, we played the roles of siblings with a good relations.h.i.+p.

There was no way we could let Dad or Ms. Yuni know about our previous relations.h.i.+p and cause them regrets—

That was the only matter for which me and Yume could see face-to-face.

But if you turned that on its head, it meant that there was not a single other thing on which we could agree on.

After returning to my room, I started to read the novel I bought today when I heard the sound of knocking.

"Dad? What is it?"

There was no reply.

I was annoyed to be disturbed while I was reading, but I also did not want to ruin the good mood they had from the remarriage—so I slotted a bookmark to the page I was reading and opened the door.

The one standing there in the corridor was the girl I loathed the most in this world.

In other words, it was Yume.

"……What is it."
I greeted her with a tone 100 degrees colder than before.

She only snorted with a hmph, as if she was implying that that was nothing.

To speak in no unclear terms, I wanted to send this girl flying.

"There's something I want to talk about. You free now?"

"No I'm not. You should know what I bought just now."

"I know. That's why I'm here, I already finished reading it."

"Tch."

Looks like she purposely came to disturb me while I was reading.

Ever since when we were dating, this girl had always read slightly faster than me. Whenever we bought the same book and started reading at the same time, she would always end up finish reading the book just as I was about reaching the climax of the story.

How underhanded.

That's what I hate about her.

Thank goodness we broke up.

"……What do you want. Spit it out."

"Let me in. I don't want to let them hear."

"Tch."

"How about you don't click your tongue over every single thing?"

"I'll do so if you'd just disappear from my sight."

"Tch."

I carefully checked the corridor to make sure that neither Dad nor Ms. Yuni were around before letting her in.

Yume looked downwards and entered my room.

"What a filthy book-filled room. It feels like I'm becoming dirty just by being here."

"That isn't what you said the other time you came over when Dad went on a business trip though. 'Wow……! What a collection!', was it?"

"That is a thing of the past. Currently, all I feel from seeing that entire collection of Sherlock Holmes on that shelf is nothing but irritation."

"Then go ahead to drop dead. Go jump off a waterfall and say h.e.l.lo to Professor Moriarty for me."

I heaved a sigh and sat down on the bed half-covered in books.

"So, what do want to talk about?"

"I'm nearing my limit already."

Yume spoke coldly while still standing.

"I can't stand it anymore—Just how much longer do I have to bear having you call me so familiarly by my first name?"

I furrowed my eyebrows.

There was no need for me to hide my displeasure at her.

"I can say the same for you. Aren't you also calling me by my first name."

"That I can still bear with. But, I just can't stand having someone like you call me by my name. I haven't even allowed that when we were dating—during middle school."

So, she doesn't even want to speak of 'when we were dating', I see I see.

"There's no other choice since we have the same surname now, isn't it. How else should I call?"

"There's another option, isn't it?"

"Which is?"

"'Big sister.'"

……What?

"Since we're siblings now, there's nothing wrong with you calling me 'big sister', isn't it."

"No no no, hold on a minute."

I had to hold my head with my hands.

"Call you? Big sister? ……Stop being ridiculous, shouldn't it be the other way around instead."

"What?"

"It's 'big brother'. That's how you should call me. It's obvious that I'm the elder one."

What kind of nonsense is she spouting now.

"……My my. It appears that most of your brain cells has gone to sleep, my this younger brother."

"How about you go to sleep. Forever, that is."

"How about I, placed in the top 100 ranking of the national exams, explain it to you in no unclear terms. Listen carefully."

This girl excelled in math more than the languages, a behavior unbecoming of any bookworm. Unforgivable.

She raised her index finger in a pose like a teacher's.

"The one who is born earlier would be the elder sibling. That is the first conjecture. And I was born earlier than you. That is the second conjecture. Thus, I'm the elder sister. End of proof. Understood?"

Her area of specialization was more logic rather than arithmetic, but there was something I couldn't let pa.s.s.

"……If my memory serves me right, our birth date seems to be on the same day, however."

That's right, this was another one of G.o.d's trap.

This girl's birthday was on the exact same date as mine.

Which wasn't to say that we were fated for each other, but we did agree on the repulsive notion of celebrating our birthdays together, and I can't say there wasn't memories of us exchanging presents as if in a devilish ceremony. Anyway, those memories were now in the trash bin.

"That's why there's no such thing as an elder sibling between us."

"I remember clearly declaring to you that 'm the elder sister though."

If you were to ask me, I'd prefer a younger stepsister over an elder stepsister. Not that I have any ulterior motive, that is.

"In any case, there's no denying the facts. It is only the date which matches—you can't say the same about the time of birth."

"Time of birth?"

"I've already looked into it."

Speaking like a detective towards a suspect, she brought out her smartphone and shoved the screen before me.

"Look at this."

The screen showed the picture of a baby. And under the picture were several words.

"Your time of birth was 11.34am."

She slid her finger across the screen to bring up the next image. Similarly showing the picture of a baby, she pointed to the clock photographed in it.

"And as you can see from this picture, I was born at least on or before 11.04am. Thus, I'm the elder one by at least 30 minutes. Now you get it?"

…………Is this girl serious.

For the sake of something like this, she had gone through the picture alb.u.ms in my house just to find the time of birth.

"Way too creepy."

When I honestly stated my opinion, she instantly turned red.

"Wh-…… Why!? The perfect evidence is needed for a flawless deduction, isn't it!?"

"There it is, that obsession for cla.s.sical mysteries. If you like puzzles so much, why don't you just go do some?"

"Uwaah! You totally said it! You just totally dissed cla.s.sical mysteries, didn't you!!"

"Well, before we even decide if your way of deduction was even fair or not, I regret to inform you that there was a hole in your argument."

"What hole! You mean to say holes like where your eyes should be!!"

I stated my reb.u.t.tal to this mystery geek (the kind who ignores the challenge to the readers) who had turned into her angry mode at me having hit the bullseye.

"You mentioned 'the one who is born earlier would be the elder sibling'—but that's where you're wrong. Since ancient time in j.a.pan, the half of the twin which was born earlier is the one to be the younger sibling."

"Eh? Why is that so?"

Yume slightly tilted her head with a look of interest on her face.

"There are many explanations such as the first one to be born serving a herald for their elder brother or sister, or that the one to be born later had spent a longer time in the womb. But anyway, the two of us stepsiblings who were born on the same date are equivalent to that of twin, meaning that you as the one who was born earlier is the younger sister. Any objections?"

"W-we…… we are not twins however……"

"If that's your argument, then we may as well not be sibling, just fellow children from previous marriages."

"Uu…… uuuuu……"

She grunted vexedly as she glared at me. Hahaha. Do your best to look up the more mature me.

"……Wait a second."

"Not waiting. Get out my room now."

"What you just said about twins only applied to the past, right? Now, it is the one who was born earlier……"

"Tch. Why don't you just get tricked obediently."

"Ah!! You were trying to trick me, weren't you!?"

"Whatever, I'm the elder brother. There, QED. That's all."

"I'm the elder sister! It freaks me just imagining that I would be your younger sister!"

It turned into a glaring contest between us. It would not be an exaggeration to say that there were sparks flying between us gazes. It was as if our gaze were crossing swords in a manner like Yamada Fuutarou's works, ready for blood to spill.

Seeing the dangerous glint in her eyes getting stronger, as if the spirit of Amakusa s.h.i.+rou was about to descend into her, I heaved a sigh to renew my spirit.

"……There's gonna be no end to this if we just glared at each other. Why don't we decide this in a civil manner through a game or something."

"It p.i.s.ses me off that you would be the one to say that, but I must agree."

"So how? Shall we decide with rock-paper-scissors, drawing lots or a coin toss?"

"Hold on."

"Not holding on. Get out now."

"And stop adding that to your sentences so automatically."

Oops. Seems like I forgot to cut the auto-reply.

Yume placed her hand to her mouth as she pondered, 'Let's see.'

"……Since we're going to do it, how about we go with this?"

"My feelings of a complete refusal is overwhelming, but luckily for you I'm a civilized human being. Let's hear it at least."

"You just can't stop p.i.s.sing me off…… For the foreseeable future, the two of us has to conceal our history and pretend to get along relatively well at least on the surface, right?"

"Much regrettably."

"We might be doing fine for now, but someday, one of us is going to blow the cover—in other words, doing or saying something that does not befits what a stepsibling would. The one who does so then is the loser, how about that?"

"Hmm…… Is that alright with you?"

"Why?"

"If that's going to be the rule, then I'll be the winner no doubt."

"You're ridiculing me, aren't you!"

That was just my truthful appraisal with the available current evidence however.

"……Well, I'm fine with this. It's not like it's not already part of what we have to do anyway. ……By the way, is this rule still in effect even when Dad or Ms. Yuni is not around?"

"Of course. It has already began."

"I see. The one who doesn't behaves as a proper stepsibling loses, huh."

"One time and it'll be over. We'll decide what it means to be a younger brother or sister at that time."

"Guess there's no meaning unless it's sudden death. Okay, I'm on."

"Then, from this moment—we'll start!"

We meet our hands in a high-five—and then.

Yume walked over to one of my bookshelf all of a sudden and started digging for something like she owned the place.

"Hey…… what the h.e.l.l do you think you're doing!?"

"Eh? There's nothing to panic about, right? Since we're siblings and all."

Seeing her grin with a malicious glint in her eyes, I realized too late the meaning behind our contest.

To speak of what would be normal between siblings would be hara.s.sment, but not without reason. That's what it would mean to not 'behaves as a proper stepsibling'.

In other words, this rule was a free pa.s.s to annoy as you please.

T-this woman……! Did she propose this rule just for this! Her personality is rotten to the core!

The only kind of guy who'd fall for her could only be someone as twisted as she was!

……This is bad!

As I glared at her taking out books at random while letting out comments like 'hmm' or 'heh' or 'uwaa' of the like, I felt a sense of foreboding creeping up my heart.

Even though it felt unpleasant for her to look through my bookshelf as if she was peeking into my mind, there was nothing too troubling even if seen fortunately. The worst would be some slightly erotic light novels.

The problem laid next to that bookshelf…… in the drawer of my study desk.

That was my only pandora box to say, which contained the notebook with my self-written novel, a certain something I bought from the drugstore and—the present I received from this girl while we were dating!

If she saw that—

'Uwah, you're still keeping this? Could I be that you still have some lingering attachment towards me? Can you stop, seriously! That's so creepy!'

—There's not a s...o...b..ll's chance in h.e.l.l I can let her see that!

At this rate, her interest is going to turn towards that desk with time. I need to find a way to redirect her attention, and in a way that is not suspicious amongst stepsiblings at that!

I squeezed my brain cells dry in order look for a way out of this conundrum. This might've been the only time since the high school entrance examination that I've strained my head this much.

As a result—I reached a method to make use of this 'sibling rule'.

"—……Just let me off already."

At my feeble voice, Yume turned around.

I stood up from my bed and approached her. Her face was colored with surprise as she looked up at me.

"I no longer want to bicker with you……"

"Eh……"

Her eyes widened slightly, my figure reflected in her pupils.

"I'll apologize if I made you mad. I disappear from your sight, so…… let stop doing all these things, okay."

I placed my hand on her shoulders as I said so gravely.

Her eyes wandered around for a moment before they settled down straight at me again.

Her large eyes wavered subtly. As she stared into my face, the hesitance in her expression gradually slip away.

And those eyes eventually focused onto one point back at me—

"…………Irido…………"

"There, you're out."

"Huh?"

I returned a grin at her who had her mouth hanging in astonishment.

"Siblings don't call each other by their surnames."

Like a cup of hot water with a tea bag thrown in, her face progressively turned crimson.

I had purposely reminded her of our past relations.h.i.+p—she finally seem to realize that that was the sure-win method of this contest.

"N-no…… t-this means that…… you're out also."

"How so? It's totally natural to say that I don't want to bicker anymore, right. We're siblings after all."

"Aaaaah……!! Uuuuuuuuu……!!"

I look down at my younger stepsister in satisfaction as she clutched her head in mortification.

"Now then…… you shall be my younger sister as promised."

"W-what…… do you plan to do?"

"Why are you hugging yourself as you step away. Just what do you think stepsisters are."

I wanted to shame her to my heart's content, but I knew my limits. Guess I'll leave turning her into my cat-eared stepsister maid for another time.

"Let's go with something simple as a start. It's time to change how you address me."

"I-in…… in what way……?"

"In an endearing manner."

I'll turn you into the ideal younger stepsister as I desire. Gahaha! This pleases me! (I say as I pour red wine into my mouth.)

Yume grumbled with a, 'Uuu……', and held her hands to her chest tightly as her eyes swim around. Then, she looked up at me with her face as red as a tomato.

Her lightly s.h.i.+vering voice reverberated in my eardrums.

"De…… dearest big brother……"

I turned to my back.

"O-out! That reaction is an out! No normal sibling would be embarra.s.sed just from being called."

"……I'm not embarra.s.sed."

"Yes you are! How long do you think I've been looking at you!?"

"Who knows. Are you sure you didn't get the wrong person. I've only met you since a few days ago."

"No fair! No fair no fair no fair no fair!!"

I persistently refused to face Yume who was stamping her feet in frustration like a child. It was definitely not because my face was feeling hot and that my pulse is quickening, or that I wanted hear her call me that again. Anyway, I just refused to meet her gaze.

Even now, Yume was grumbling and raising a ruckus.

"Yume? What's with all that noise?"

We could hear Ms.Yuni's voice coming from below. That to me was my salvation. A smile formed on my face as I announced my victory.

"Time's up."

"G-grrrr……!"

"Well, if you'd learnt your lesson, then stop trying to meddle into my business. Don't be mistaken just because you've read lots of mystery novels. There's a clear distinction between you and me over here."

Over here, I tapped my temple.

Whether it was because of rage or frustration, Yume's face turned more and more crimson as tears welled up in the corner of her eyes.

"………………You were never so unkind in the past…………!!"

……Don't you cry, you coward.

I fiddled with my hair as the atmosphere got somewhat awkward.

……Did I go too far, perhaps? For people like us, to make fun of a genre was pretty much a personal attack. To do something like rummaging through the bookshelf of a criminal and criticizing their choice of reading as the ma.s.s media does was indeed going to far……

I heaved a sigh and grudgingly and ever so reluctantly stretched out my right hand—and gently brushed her head.

"Fine fine, I apologize. I was in the wrong. Okay, big sister."

Somehow, it felt nostalgic. In the past, whenever something happened, I would always see Ayai making this bashful expression—

However, the current Yume was not being bashful or anything.

Her whole body was s.h.i.+vering, much like a volcano on the verge of eruption—

"………………That-"

"That?"

"That's…… the part of you! I just hate how you can always do things so easily!! You s.h.i.+tty big brother!!"

Shouting that novel barb, she ran out of the room knocking over a few towers of books.

I stood at the same spot in a daze.

……I have never seen that side of her before while we were dating.

"……Jeez……"

—If you're gonna say that.

Then even those parts of you—the part which is reserved yet hates to lose, somewhat mature but still so childish…… and in the time I forgot, you learnt to make a face I've never seen before—

—Those are the parts I hate about you.

⯁

In the end.

"……Good morning, Mizuto."

"……Good morning, Yume."

The way we called each other did not change.

In the first place, there was a contravention in the rule where we were to decide who was the younger sibling only once. If not, we would end up in a weird situation where we took turns calling each other older brother or sister.

Speaking of what has changed—

"Mizuto, can you pa.s.s the soy sauce?"

"Sure, here you go, Yume."

As I pa.s.sed her the soy sauce, our gazes overlapped for a second.

—There's no way I'm going to be your younger sister.

—What a coincidence. I also absolutely reject being your younger brother.

And so we exchanged thoughts without words.

I just can't come to terms with this girl. There must have been some mishap in middle school which had caused our minds to go haywire. That was the one thing I had elucidated from yesterday.

As we sat around on the dining table enjoying our breakfast, we were trading low kicks under the table. Next to us, Dad and Ms. Yuni were talking harmoniously with joyous smiles on their faces.

The only ones who knew of the real relations.h.i.+p between us were the two of us.

That our most greatest nemesis would be a family member living under the same roof.

……Nevertheless.

"Yume, pa.s.s me back the soy sauce."

"Here, Mizuto."

For the two of us who had stuck to using our last names while we were dating to be now calling each other by our first names—G.o.d that b.a.s.t.a.r.d sure has a twisted sense of irony indeed.