My Clingy Yandere Stepsister Turned Out to Be My Ex’s Twin Sister [Dropped] - Chapter 03: A Kiss on the Way Home, A Reunion in the Classroom

Chapter 03: A Kiss on the Way Home, A Reunion in the Classroom

Our family dinner with my dad’s fiancée and her daughter wrapped up around 9 PM.

From what I could tell, my new stepmom, Mariko-san, didn’t seem like a weird person.

(At least, not compared to my dad.)

“Alright, Ryota! Mariko-san and I are gonna hit the bar for some drinks, so you take Yuzuki-chan home, yeah?”

Dad grinned as he spoke in front of the hotel.

“T-Tetsurou-san… isn’t it a little dangerous to send two kids home alone?”

Mariko-san turned to him with concern.

Yeah… that was a pretty reasonable reaction.

“It’s fine, it’s fine! They’re high schoolers, not little kids. Right, you two can handle it?”

“No problem.”

I was already used to Dad’s hands-off parenting style, so it didn’t bother me.

“Great! Yuzuki-chan, see you later!”

“Yes, see you!”

Yuzuki, my soon-to-be stepsister, waved at him with a smile.

“…”

Yuzuki Iida.

The girl who was about to become my sister.

She was the same age as me.

Starting next semester, she’d be attending my school, Alpico Academy.

And the more I looked at her…

The more I realized just how much she resembled Mishiro.

My ex-girlfriend, Mishiro Azusagawa.

“Um… Onii-san?”

Yuzuki tilted her head, looking up at me.

“Is something wrong?”

“Ah, no… it’s nothing. Uh… let’s head home.”

Yuzuki nodded and followed closely behind me.

…To be honest, I had no idea how I was supposed to act around her.

Legally, she was about to become my stepsister.

But she was also my age.

I couldn’t just flip a switch and suddenly start treating her like family.

“Fufu~ Onii-san♡”

She peeked up at me with a playful gaze, standing way too close for comfort.

My heart skipped a beat.

“Uwoah!”

I instinctively stepped back.

“No need to be so startled. It’s not like I’m going to eat you or anything…♡”

Yuzuki giggled—soft, teasing, almost seductive.

God…

She looked so much like Mishiro.

My ex was sweet, kind, and never did anything to catch me off guard.

Yuzuki, on the other hand, seemed to enjoy my reactions—like she was having fun teasing me.

…Was she S or something?

“I get that this is confusing for you. But honestly… I don’t like how formal you’re being. We’re family now, after all.”

Her voice softened, almost as if she were… sad.

Did she think I was rejecting her?

Like I was pushing her away before she could even get close?

That wasn’t what I was trying to do, but… I could see how she might take it that way.

“R-Right… I guess so. My bad. Ah, I mean… sorry.”

“It’s fine, Onii-san. But… can you stop speaking so formally? And please, just call me by my name.”

“I mean… that’s a bit much…”

“Please?”

Yuzuki leaned in even closer.

Her sweet scent filled my senses, and with her face so near, my heartbeat spiked.

Then—she moved in even closer.

“W-Why are you getting so close?! We’re in public, you know?!”

It was late at night, so there weren’t many people around.

But that didn’t mean the streets were completely empty.

From an outsider’s perspective, it probably looked like I was getting way too close with a beautiful girl.

“What exactly are you so worried about, Onii-san?

Yuzuki pressed her body against mine, whispering softly into my ear.

“…I am your little sister now. Isn’t it normal for siblings to get along?”

…Why?

Why did she look so much like Mishiro?

Her face, her voice… everything overlapped with the girl who dumped me.

It was messing with my head.

“J-Just move away already!”

“Then, call me Yuzuki.”

“F-Fine… Yuzuki. No more formal speech. You’re my sister. Happy now?”

Chuu♡

“Wha—!?”

Yuzuki suddenly pulled away, giggling.

My cheek burned. A lingering, wet sensation remained on my skin.

D-Did she just—!?

“W-What the hell are you doing?!”

“A kiss, of course. A sibling kiss. You know, like the ones kids give each other?♡”

SHE JUST STRAIGHT-UP KISSED ME.

We were OUTSIDE.

IN PUBLIC.

And she acted like it was completely normal.

“D-Don’t be ridiculous! Siblings don’t just k-kiss like that!”

“Oh? But I used to do it all the time with my Onee-san.”

“Onee-san…?”

Yuzuki nodded with a soft “Mhm.”

“A long time ago, I had an older sister. We always gave each other affectionate little kisses~♡”

…Wait, Yuzuki had a sister?

Something about that didn’t add up.

“Mariko-san has another daughter besides you?”

“Yep. My sister. But… after our parents divorced, she went far away with my dad.”

I see… Mariko-san had been married before.

And when she and her ex-husband split, Yuzuki’s sister went with him.

So they were separated.

“Sorry for making things all depressing, Onii-san.”

“Ah, no… I should be the one asking—aren’t you lonely?”

“Of course, I am. But… it happened when I was little. And besides…”

Yuzuki ran her tongue over her lips—slowly, deliberately.

“Now, I have such a wonderful Onii-san…♡ Handsome, kind, so… amazing… Ahh~♡”

Her gaze softened into something dreamy, like she was looking at a crush—or someone she idolized.

Like she was completely in love.

“…You’re misunderstanding things.”

I took a deep breath and told her the truth.

That night—I didn’t save her out of kindness.

It was just a knee-jerk reaction.

I only stepped in because, for a split second, I thought she was Mishiro.

“It was just a coincidence.”

But Yuzuki simply smiled and shook her head.

“Even so, my feelings won’t change. The debt I owe you for saving me… I will never forget it. Not for the rest of my life.”

There was something dangerous about Yuzuki.

The way she spoke about debt and never forgetting…

It felt off.

…But.

Somewhere deep inside, a part of me didn’t hate it.

At the time, I couldn’t understand why.

But that was only natural—because back then, I still didn’t realize the connection between Yuzuki and Mishiro.

“Look, cut that out already. Seriously.”

It’s not like I disliked Yuzuki as a person.

But just looking at her made my chest feel tight.

“Do you hate me?”

“It’s not that… Just act normal, alright?”

But Yuzuki only smiled, her eyes gleaming.

“That’s impossible. Because I… love you more than anyone else in the world, Onii-san♡”

She took my hand and squeezed it—tight.

“So please… take good care of me, my dearest Onii-san♡”

★

A few days after my dad’s remarriage, the second semester began.

Classes were back in session.

Dragging my feet, I made my way toward the classroom.

Inside, sitting at her usual seat—

Was Mishiro.

“”…””

Neither of us said a word as we quietly took our seats.

Luckily, I sat by the window while Mishiro’s seat was near the hallway—far enough that I didn’t have to sit through class feeling awkward.

…Even so, I couldn’t stop my eyes from drifting toward her.

Some part of me was still caught up on her.

Her long, silky black hair. That calm, graceful presence.

She was still beautiful.

“A kiss, of course. A sibling kiss.”

Damn it. I couldn’t get Yuzuki’s kiss out of my head.

A part of me was desperately trying to justify myself to Mishiro in my thoughts.

But… did I even need to? 

She wasn’t my girlfriend anymore.

We were over.

And then—

Ding-dong, ding-dong…

“Alright, everyone, take your seats.”

Our homeroom teacher, a female instructor, walked in.

The classroom instantly quieted down as the students returned to their seats.

“Today, we have a transfer student to introduce. Come in.”

At the teacher’s signal, the door opened.

And the one who stepped inside was—

Yuzuki.

My brand-new stepsister.

“Whoa! She’s gorgeous!”

“Dude, no way, she’s crazy hot!”

“YES! Finally, a beautiful transfer student!”

The guys in the class were losing their minds.

Not that it had anything to do with me.

I already knew she was transferring here, so I wasn’t particularly shocked.

And besides—

She was my stepsister.

So there was no reason for me to get all worked up over it…

“…Yuzuki!”

From across the classroom, Mishiro suddenly shouted.

“Yuzuki! It’s you, isn’t it?!”

“…Azusagawa-san?”

Ignoring the stunned teacher and the murmuring classmates, Mishiro ran forward.

She threw herself at Yuzuki, wrapping her arms around her.

“I missed you! Yuzuki! I missed you so much…!”

…What the hell?

She was acting like she had just reunited with a long-lost sibling—

And then, it clicked.

A few days ago, Yuzuki told me she had an estranged sister.

No way. No way.

Mishiro… was Yuzuki’s twin sister?!

But if she’s the older sister, then why are they in the same grade…?

“It’s been so long, Onee-san. I’ve wanted to see you for so, so long.”

Yuzuki returned the hug—

But her eyes…

For some reason, they felt cold.

★

Yuzuki Iida—Ryota’s new stepsister—had just reunited with her twin sister in the classroom.

Mishiro ran straight toward her, tears streaming down her face as she embraced her.

For any normal person, this would be a heartwarming moment.

A long-separated family, reunited at last.

A moment to be cherished.

But Yuzuki knew the truth.

She knew that her beloved Onii-san had been dating this girl—

Up until just a few days ago.

“…how dare you… Onee-san.”

“Eh?”

Yuzuki whispered under her breath.

But it was too soft for Mishiro to hear.

Then, as if nothing had happened, Yuzuki’s expression shifted into a bright, cheerful smile.

The kind of smile a younger sister would have when reuniting with her long-lost sister.

“It’s been so long, Onee-san. I’ve wanted to see you for so, so long…”

For Yuzuki, Mishiro wasn’t just her long-lost twin sister.

She was the girl who stole Onii-san’s firsts—the one who took the place Yuzuki had always wanted.

People say men want to be a woman’s first love, while women want to be a man’s last love.

But Yuzuki was different.

She wanted to be Ryota’s first.

She should have been his first kiss, his first love, his first everything.

And yet—

Mishiro took that from her.

How far did you go with Onii-san?

Did you kiss? Hold hands? Sleep together?

A deep, seething jealousy bubbled inside her, black flames licking at her heart.

She turned her head.

Ryota was staring in her direction.

But then—

She noticed something.

He wasn’t looking at her. He was looking at Mishiro.

…Why? 

Ah. So he still wasn’t over her.

How simple.

If he couldn’t forget—

She would make him.

She would erase Mishiro from his mind completely, make him hers in every possible way.

She would love him so much that he wouldn’t even remember her sister’s name.

With her body, her face, her voice—

She would devour him, until he was hers alone.

She would never let her sister have him again.

At first, she thought she could take things slow.

But now?

She wasn’t going to hold back anymore.

She would take everything from him.

Every last piece.

Neither Mishiro nor Ryota had any idea—

Of the dark, unwavering desire that had just taken root inside Yuzuki’s heart.