My Stepsister is My Ex-Girlfriend Volume 1 Chapter 1

Editor: PF

The Ex-Couple Refuse to Call – “That’s exactly what I hate about you.”

“……………………”

“……………………”

I was standing at the entrance to my home, stuck in a staring contest like some kind of hoodlum.

My opponent was a girl of my age. There was nothing else between us─ or so I’d like to claim, but there was something between us. Perhaps I should say there used to be something.

“Where do you think you’re going, huh, Mizuto?”

“That’s my line. Where are you going, Yume?”

We exchanged words, then silence. For the third time already.

In fact, I already knew where she was headed even without asking. It was the large bookstore in front of the station. A certain mystery novel publisher released their new books today. I planned to pick up one of their new series, and this girl had the same idea.

That’s why we’d probably wind up leaving together, walk side-by-side to the bookstore, head to the same corner inside, and line up before the register together.

Wouldn’t we totally look like a couple with the same taste in books? That was exactly what both of us wanted to avoid.

Basically, we were stuck in a deadlock.

We couldn’t leave the house together, but as to the question of who would get to leave first, well… That’s what got us into this situation.

Why didn’t we just talk it out, you ask?

Because that was impossible. There wasn’t a single thing that could ever be solved through conversation with this girl.

“─Eh? What’re you two doing?” Yuni came over from the living room, dressed in a suit. “Weren’t you two heading out?”

She was none other than the person who became my mother just one week ago. In other words, she’s the woman who married my father—and the mother of the girl in front of me.

“I was just about to,” I said. I’d planned to follow up with a ‘see you’ and smoothly seize initiative, but Yuni interjected before I could.

“Oh! Are you going to the bookstore?” she said. “Your dad told me you’re quite the bookworm. Going the same way as Yume, right? She only ever goes out to the bookstore or library.”

“Err…”

“Come on, Mom,” Yume said, looking annoyed.

“Oh, how stupid of me! Are you two going together? I’m so glad you’re getting along. Please look after Yume, Mizuto. She’s rather shy, after all.”

“S- sure.” I couldn’t do anything but nod. At the same time, I felt an icy glare from beside me.

“Well, I’ll be leaving now. Have a safe trip, both of you. Get along as siblings, okay?” And with that, Yuni disappeared beyond the entrance.

Leaving behind me and her─ siblings. Brother and sister, but only by law. And as fellow stepchildren─

“Why’d you have to nod?” Yume asked.

“How could I say no when she asked me like that?”

“And why should I have to get along with someone like you?”

“Who cares? You think I wanna get along with you?”

“This is what I hate about you,” Yume said. “You damn otaku.”

“And I hate your self-centeredness, you damn nerd.”

Our parents never knew the real relationship between the two of us. Only she and I knew,

that I, Irido Mizuto─

and her, Irido Yume─

─had, until two weeks ago, been dating.

⯁

In my second and third year of middle school, I had something that resembled a “girlfriend”. In hindsight, you could more accurately say it was a folly of youth.

If you asked me when we first met, it was near the end of July, right at the start of summer break. It was during an early afternoon in the library. She was standing on a stepping stool, trying to reach the topmost row of the bookshelf.

As the situation was so clichéd, I’m sure you can imagine what followed, but I’ll tell you anyway.

I grabbed the book for her.

If I could travel back in time, I’d tell myself to leave that girl alone.

But I didn’t know anything back then, and when I saw the title of the book she wanted to read, I asked her, “Do you like mystery novels?”

I wasn’t a fan of mystery novels in particular. If anything, I was the sort who’d read everything─ pure literature, romance novels, light novels, I read them all without reserve. So I’d already read that particular novel.

It wasn’t a book I was enthusiastic about. But still─ and this probably owed to me being a bookworm─ I couldn’t help but be excited about someone picking up a book I’d read before. It was somewhat like a bull being agitated by a red cloth, or kinda like an instinct you couldn’t control… and probably a trap from God.

In other words, it was fate.

And through that fated meeting, the both of us found kindred spirits in each other. We’d meet in the library over the course of the holiday; there was practically never anyone else around. By the end of summer break, in late August, she confessed to me.

And that’s how, for the first time in my life, I got something that resembled a ‘girlfriend’.

Her name was Ayai Yume.

Well, at the time, at least.

Back to the here and now… I don’t feel I need to spell it out, but that was the start of trouble.

In fact, the chances of a middle school love confession not ending in drama was around five per cent or lower. You don’t really see any middle school couples go on to spend the rest of their lives together.

But the two of us were sure we’d buck the trend.

Neither Ayai nor I were the type to stand out much in school, so our relationship proceeded uneventfully. We’d act like we didn’t know each other in public, but then we’d have a date in a corner of the school library, or we’d go to a bookstore, and in the weekends we’d go to a café or the public library. Our love blossomed as we indulged in our interests together.

Of course, we also did stuff normal couples did.

Ayai didn’t speak to anyone in class, owing to social anxiety. Some said she was mature, while others called her gloomy. So while we didn’t go as quickly as most, we still went on dates, held hands, and shared awkward kisses.

There wasn’t anything strange about us, and our relationship developed just as any other.

Our first kiss was at the fork on the way home from school, under the glow of the setting sun. Ayai’s smile and slightly flushed cheeks, right after our kiss─ more like our lips grazed each other─ was still vividly in my mind.

Right now, that memory just brings to mind one thing.

Screw you.

Either to that girl, or myself at that time.

… Anyway, that’s how our relationship steadily progressed. The turning point came after we became third years. The trigger was Ayai growing out of her social anxiety.

Over the course of our relationship, Ayai’s anxiety lessened, and she made numerous friends in her new class. Her progress was remarkable; unlike when we were in second year, Ayai was never without partner during gym class.

Ayai herself was tremendously happy about the change, and on the surface I was happy as well and celebrated with her.

That’s right, I only felt like that on the surface.

But inside, well─ I regret how that went. Even while I praised her for growing as a person, the feeling of wanting to keep her all to myself grew inside me.

I should’ve been the only who knew about how cute she was, how cheerful she could be. Her smile should’ve been only for me, and so forth and so on.

But that was wrong of me.

That feeling bled into my words and actions. And without even knowing why, Ayai started trying to appease me. That only got on my nerves more.

I’d known, of course. Although I could blame the way Ayai’d changed because of her personal growth, the real reason was my petty desire to monopolize her. She hadn’t done anything wrong; the fault lay with me.

However. Despite that.

Let me say something in my defense. When I’d realized how stupid I was being, I apologized to her. I’d become jealous because of this and that, I’m sorry for taking it out on you. I’ll make it up to you, please give me another chance, etcetera, etcetera.

And then. What do you think she said?

“Oh, so you dislike it when I get close to other guys, but it’s fine for you to flirt with other girls?”

Huh?

Who could blame me for replying like that?

According to her, I’d cheated on her with another girl in the school library where we’d first met─ that was news to me. I told her, she’d probably misunderstood when I was talking with a member of the library committee or something, but Ayai kept insisting I’d cheated on her and wouldn’t listen to reason.

In the end, I kept on apologizing.

What the heck?

I admit, 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. I understood that.

But why should I have to be admonished for her baseless misunderstanding?

Okay, hang on, I know that in the heat of the moment, you can say things you’ll regret. After all, that’s what I did, so I apologized for it. And in that case, shouldn’t she do the same, too? How could it be that I was the only one to have to apologize for being unreasonable, while she didn’t feel the slightest bit sorry? That was just wrong.

—And with those feelings, we patched things up and continued dating for a few months afterwards.

However—a glass, once broken, can never be the same again.

The things we used to like about each other, were now things that annoyed us. We started being sarcastic with each other, and replying to each other’s text messages just became a pain. The lack of reply just 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. Neither of us had the courage to do something about it.

We were merely clinging on to the happy memories we’d made before.

But when Valentine’s Day came, and we didn’t exchange even a single word, it was obvious—there was no further point to this. The two of us understood that even before we talked.

During the graduation ceremony, I took the initiative and raised the issue.

“Let’s break up.”

“Yeah.”

It was over just like that. Neither of us cried about it. She didn’t even look angry, more like she’d been anticipating it. I thought that I probably looked the same.

She was the girl I had liked and treasured so much…

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

… I must say, love is but a momentary stupor. I had finally freed myself from that beguilement—

And so, I graduated middle school with a light heart, like a heavy load had been taken off my mind.

Then came that night.

My father broached the subject with a serious face.

“Mizuto, your father thinking of remarrying.”

Whoops.

Looks like humans never stopped worrying, no matter how old they’d get. I did feel sorry for Dad, since he had had to raise me by himself, so I didn’t object. In fact, I’d welcome remarriage. So go ahead, do as you please.

Besides, I’d just completed compulsory education. I was feeling great. Which is why I was so open-minded to what Dad said next.

“She already has a daughter. Do you 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 hyped. Thinking back on it, I’d been too excited.

So, when my stepmother-to-be came to visit, it felt like I’d just had a bucket of ice-cold water dumped over me.

“…………”

“…………”

Because the daughter she’d brought along was none other than Ayai Yume.

Correction.

By that time, she had become Irido Yume.

We stared at each other with open mouths, and surely we were shouting the same thing in our mind.

—Damn you, God!!

And so, my ex-girlfriend became my stepsister.

⯁

“… Dinner was delicious.”

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

… Dammit. What bad timing. I had also just finished dinner. It would be weird of me to just sit down here.

“Dinner tasted great.”

I also stacked my tableware and brought them over to the kitchen—where Yume was washing her dishes.

Her annoyingly long jet-black hair was combed neatly.

She shot a glance at me but didn’t say a word. She just continued cleaning.

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

If possible, I would’ve liked not to line up next to her, but it’d be a problem if we started avoiding each other. After all—

“And here I’d been worried about them becoming siblings at this age,” Dad’s voice came from the living room. “Thank heavens, looks like they get along just fine.”

“It’s true! Yume and Mizuto went to the bookstore together earlier today. Having a hobby in common must surely help them bond,” Yuni said.

“I kept fretting over it, but guess I can breathe easy now.”

They were sure having a joyous talk back there.

The remarried couple seemed to live in happiness everyday—in stark contrast to their children.

“… You get it, right?”

Yume spoke so softly, that the flowing water from the tap almost drowned her out.

“Get what?” I said.“Don’t ever make those two regret their marriage.”

“I know, I know. I already planned to take our little secret to the grave.”

“Good.”

“… Everything about you is so obnoxious. Just how did you turn out like this?”

“If I used to be different, then how I am now is one-hundred percent your fault,” Yume said.

“What?”

“Was that too hard for you?”

“Hey! What’re you two talking about?” Dad called from the living room.

We instantly played nice.

 “Oh, nothing much,” I said. “We were just discussing the novel we bought earlier, y’know.”

“Right, we were just discussing the novel,” Yume said brightly, while kicking me against the shins.

“—Ouch.”

“What’d you add ‘y’know’ for? Do you even know how to language?” Yume said in a low voice.

“Don’t you worry about that. I actually score in the top 100 nationally,” I retorted.

“… Grrrr, I can’t believe I used to praise you for that.”

“How do you think I feel? I used to be happy hearing your praise.”

In public, we played the roles of siblings who got along well.

We couldn’t possibly let Dad or Yuni find out about how we used to date, and make things awkward for them.

That was the only thing Yume and I could see eye-to-eye on.

But if you flipped that on its head, it meant there wasn’t anything else we agreed on.

After returning to my room, I started to read the novel I bought today, when someone knocked on the door.

“Dad? ‘Sup?”

There was no reply.

It was annoying to be disturbed while reading, but I didn’t wanna ruin their just-got-married high. I placed a bookmark for 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 do you want?” I said, my voice a hundred degrees colder than before.

“Hmph.” Yume snorted, as if she didn’t care.

Just to be clear, I wanted to punch her.

“There’s something I want to discuss. You free?” Yume said.

“No, I’m not. You already know I bought a new novel.”

“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.

This girl had always been a faster reader than me. Whenever we bought the same book and started reading at the same time, she’d always finish the book just as I reached the climax of the story.

How underhanded.

That’s what I hated about her.

Thank goodness we broke up.

“… Spit it out, what do you want?”

“Let me in,” Yume said. “I don’t want them to hear.”

“Tch.”

“How about you stop clicking your tongue over every little thing?”

“I’ll stop it, just get out of my sight.”

“Tch.” This time, Yume clicked her tongue.

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

Yume looked down and entered my room.

“What a filthy book-filled room,” Yume said. “I feel dirty just standing here.”

“That’s not what you said last time you came over, when dad was on a business trip. ‘Wow, what an amazing collection!’… right?”

“That’s a thing of the past. Right now, I just feel annoyed when I see the entire collection of Sherlock Holmes lined up there.”

“Go screw yourself. Better yet, go jump off a waterfall, say hello to Professor Moriarty for me.” I sighed and sat down on the bed half-covered in books.

“So, what did you want to talk about?”

“I’m reaching the end of my patience,” Yume said coldly, still standing. “I can’t stand it anymore. Just how long do I have to suffer you calling me by my name?”

I furrowed my eyebrows. I didn’t need to hide my annoyance with her.

“Same goes for you. Aren’t you also calling me by name?”

“I can bear with that,” Yume said. “But I just can’t stand having someone like you call me by name. I didn’t even let you do it while we were da—in middle school.”

Ah, so she doesn’t even want to talk about the time we were dating. I see, I see.

“We have the same family name now, so it’s not like we have a choice now, do we?”

“There is another choice, though?” Yume said.

“Meaning?”

“‘Big Sis.’”

… Er, what?

“We’re siblings now, so it’s not weird for you to call me ‘Big Sis’, right?”

“No no no, hang on.” I had to hold my head with my hands. “Call you ‘Big Sis’? Stop being ridiculous, shouldn’t it be the other way around?”

“What?”

“You should be calling me ‘Big brother’. I’m obviously the older one.”

“Oh my. It looks like my little brother’s brain’s nodded off already.”

Just what kind of nonsense was she spouting now?

“How about you nod off? And don’t come back.”

“How about I, in the top 100 nationally for math, explain it to you clearly? Please listen carefully.”

This girl excelled in math more than languages, a trait unbecoming of any bookworm.

Unforgivable.

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

“The one who is born earlier will 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?”

It was more that she specialized in logic than arithmetic, but there was something I couldn’t ignore.

“If I remember correctly, we’re born on the same day, though.”

That’s right, this was another one of God’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 older sibling between us,” I said.

“I remember clearly declaring to you that I’m the older one, though.”

If you were to ask me, I’d prefer a younger stepsister over an older stepsister. There’s nothing behind that preference.

“In any case, there’s no denying the facts. Only the date matches—you can’t say the same about the time of birth,” Yume said.

“Time of birth?”

“I’ve already looked into it.”

She spoke like a detective would to a suspect. She brought out her smartphone and shoved the screen in my face. “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,” Yume said.

She slid her finger across the screen to bring up the next image. This also showed the picture of a baby, and 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?”

… Was she freaking serious?

For something as trivial as this, she went through the picture albums just to find the time of birth.

“You’re 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 classical mysteries. If you like puzzles so much, why don’t you just go do some?”

“Uwaah! You totally said it! You just totally dissed classical mysteries, didn’t you!!” Yume said.

“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 rebuttal to this mystery geek (the kind who ignores the challenge to the readers) who’d grown angry at me having hit the bullseye.

“You mentioned ‘the one born earlier is the older sibling’—but that’s where you’re wrong,” I said. “Since ancient time in Japan, the half of the twin which was born earlier is the younger sibling.”

“Eh? Why?” 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 as a herald for their older sibling,” I continued, “or that the one to be born later had spent a longer time in the womb. But anyway, the two of us stepsiblings, born on the same day, are equivalent to twins. Meaning, since you were born earlier, you’re the younger one. Any objections?”

“B- but we… we’re not twins.”

“If that’s your argument, then we may as well not be siblings, just fellow children from previous marriages.”

“Uu… uuuuu…” She grunted vexedly as she glared at me. Hahaha.

Do your best to look up to the more mature brother.

“… Wait a second,” Yume said.

“Not waiting. Get out of my room now.”

“What you just said about twins only applied to the past, right? But these days, it’s 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 older brother. There, QED. That’s all.”

“I’m the older sister! It freaks me out just imagining that I would be your younger sister!”

It turned into a glaring contest between us. It wouldn’t be an exaggeration to say there were sparks flying between us gazes. It was as if our gazes 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 Shirou was about to descend into her, I heaved a sigh to renew my spirit.

“… We can go on glaring at each other forever without resolving this. Why don’t we decide this in a civil manner, like through a contest or something?”

“It pisses me off that you would be the one to say that, but I must agree,” Yume said.

“So? Rock-paper-scissors, draw lots or toss a coin?”

“Hold on.”

“Not holding on. Get out now.”

“And stop telling me to get out every time.”

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?”

“Every fiber of my being wants to reject it outright, but luckily for you I’m civilized. Let’s hear it at least.”

“You just can’t stop pissing me off,” Yume said. “For now, the two of us have to conceal our history and pretend to get along, at least publicly, right?”

“To my regret.”

“We might be doing fine now, but one day, one of us’ll blow our cover—in other words, doing or saying something un-sibling-like. First to do so is the loser, alright?”

“Hmm… And you’re fine with that?”

“Why?”

“If that’s going to be the rule, then I’ll no doubt be the winner.”

“You’re ridiculing me, aren’t you!?”

Actually, that was just my honest assessment based on the currently available evidence.

“Well, whatever, I’m okay with this. Not like we weren’t already doing that,” I said. “By the way, is this rule still in effect even when Dad or Yuni aren’t around?”

“Of course. We’ve already begun.”

“I see. The one who doesn’t behave as a proper stepsibling loses, huh?”

“Mess up once and you’re done. We’ll decide the rules for being a younger brother or sister when we get to that point.”

“Guess there’s no meaning unless it’s sudden death. Okay, I’m on.”

“Then, from this moment—we’ll start!”

Our hands met for a high-five, and then─

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

“Hey, what the heck do you think you’re doing!?”

“Eh? There’s nothing to fuss 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 harassment, but not without reason. That’s what it would mean to not ‘behave as a proper stepsibling’.

In other words, this rule was a free pass to annoy the other as you pleased.

T-this girl…! 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’ or the like, sense of foreboding crept into 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 she’d find. 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 Pandora’s box, and my only Achilles’ heel. That’s to say, it 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 it be that you still have some lingering attachment towards me? Can you stop, seriously? That’s so creepy!’ she’d say.

—There’s not a snowball’s chance in hell I can let her see that!

At the rate she was going, her interest would turn towards that desk eventually. I needed to find a way to redirect her attention, and in a way that wasn’t un-sibling-like!

I squeezed my brain cells dry in order look for a way out of this conundrum. That might’ve been the only time since the high school entrance examination that I’d strained my head that 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 don’t want to keep bickering with you,” I said.

“Eh…” Yume’s eyes widened slightly, my figure reflected in her pupils.

“I’ll apologize if I made you mad. I’ll get out of your sight, so… let’s stop doing stuff like this, okay?” I placed my hand on her shoulders as I said so gravely.

Her eyes wandered around for a moment before they settled straight on 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 relationship—she finally seemed to realize that that was the sure-win method of this contest.

“N-no… t-this means that… you’re also out.”

“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 looked down at my younger stepsister with satisfaction as she clutched her head in mortification.

“Now then, as promised, you’ll be the younger sister.”

“W-what… are you planning?”

“What’re you shielding yourself and shying away for? Just what do you think a stepsister is?”

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 to start with. It’s time to change how you address me.”

“I-in… in what way…?”

“Endearingly, dearest.”

I was gonna make her behave like the ideal stepsister I desired! Gahaha! This pleased me! (I said as I poured red wine into my mouth.)

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

Her lightly shivering voice reverberated in my eardrums.

“Dea- dearest Big brother…”

“…”

I turned around.

“O-out! That reaction is an out! No normal sibling would be embarrassed just from being called.”

“… I’m not embarrassed.”

“Yes, you are! How long do you think I’ve been watching you!?”

“Who knows? You sure you didn’t get the wrong person? I only met you 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 was 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 Yuni’s voice coming from below. That was my rescue. A smile formed on my face as I announced my victory.

“Time’s up.”

“G-grrrr…!”

“Well, if you’ve learnt your lesson, stop meddling in my business. Don’t be mistaken just because you’ve read lots of mystery novels. There’s a clear difference between you and me here.” At the word ‘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 weren’t such a jerk before!”

… Don’t cry, you coward.

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

… Maybe I went too far? 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 mass media did was indeed going too far…

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

“Fine, fine, I’m sorry. My bad. Got it, Big Sis?”

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

However, the current Yume wasn’t being bashful or anything.

Her whole body was shivering, much like a volcano on the verge of eruption—

“That─”

“That?”

“That part of you! I hate how you do things like that so easily! You shitty big brother!!”

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

I was rooted in place, dazed.

… I’d never seen that side of her while we’d been dating.

“Jeez…”

—If you’re gonna say that.

Then that part of you… where you’re reserved, but hate to lose, where you’re mature and yet so childish… That part where you somehow managed to make a face I’d never seen before…

─That’s what I hate about you.

⯁

“… Good morning, Mizuto.”

“… Good morning, Yume.”

In the end, we didn’t change the way we addressed each other.

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 treating each other as the older brother or sister.

Speaking of what did change—

“Mizuto, can you pass the soy sauce?”

“Sure, here you go, Yume.”

As I passed 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 couldn’t bring myself to like this girl. Something must’ve happened in middle school, that made us go temporarily insane. That was the only thing the day before made clear to me.

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

The only ones who knew of the real relationship between us were the two of us.

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

…Nevertheless.

“Yume, pass 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—that damn God sure had a twisted sense of irony indeed.

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