+18 Extra Chapter: Kisaragi Yuna

When I was little, I used to think I would marry my brother.

I loved him more than anyone else, and I knew he loved me too.

"Yuna really loves her big brother, huh?"

"When I grow up, I’m gonna marry Onii-chan!"

Even when I declared that in front of my family, Mom and Dad only smiled, treating it as nothing more than an adorable childish fantasy.

But as I grew older, I learned that sisters couldn’t marry their brothers. So from then on, I started acting like a normal little sister around him.

…I thought things would stay that way forever.

I’ll never forget—it happened when I was in my second year of middle school.

It was a Sunday, and my family was out. I went into my brother’s room to borrow some manga.

While browsing the bookshelf, I noticed an unnatural bulge at the edge. Curious, I reached for it without thinking.

The book was just a reference guide, but behind it, there seemed to be another book hidden. Drawn by curiosity, I pulled it out—and my eyes landed on the cover: a girl with big breasts, naked, wearing a seductive expression. It was an adult ecchi manga.

My heart pounding, I sat on my brother’s bed and flipped through the pages.

It was what you’d call a "little sister" manga.

Later, I checked—out of all the adult books he had, this was the only one with that theme. The title didn’t even suggest it, so he probably bought it without realizing.

But at the time, I didn’t know that.

The story was about a heroine who got caught masturbating in her brother’s room, leading to them having sex, then struggling with their forbidden sibling relationship as they fell deeper into depravity.

The shock of reading my first ecchi manga—and the fact that my brother owned it—sent me into a panic. My head spun.

Then, my eyes drifted to the trash can.

In the manga, the heroine had masturbated while sniffing the tissues her brother used.

Since it was Sunday, Mom hadn’t taken out the trash yet—everything was still inside.

Hesitantly, I reached for the trash can… not even sure what I was doing.

There, just like in the manga, were crumpled-up tissues. I pinched one between my fingers and held it up.

When I brought it close to my nose, a pungent smell hit me, making me grimace.

Gross…

But this was the smell of semen.

At that moment, I realized—this was the strange scent that had started lingering in my brother’s room.

It was musky, definitely not pleasant.

But before I knew it, I was sniffing it over and over. Just like the heroine in the manga.

The tissue was still damp, leaving sticky traces on my fingers and nose. But instead of disgust, all I felt was the thrill of being tainted by my brother.

Inside the tissue was a thick, yogurt-like clump. I scooped it up with my finger.

A cloudy, sticky mass clung to my fingertip. I pressed my thumb against it, testing the texture—slippery, like hair conditioner. When I pulled my fingers apart, it stretched into slimy threads.

…What am I doing?

My brother and I were just normal siblings who got along well.

But what if he came onto me like in the manga? What if he said he wanted to do that with me…?

My body grew hot, my mind hazy.

Especially down there—it burned so much I could feel my panties soaking wet, like I’d wet myself.

"I’m… dripping…"

I knew about this stuff from magazines and friends.

But honestly, I’d never really understood it before. I’d never had a crush, and the idea of being with someone never clicked.

I’d tried touching myself a few times, but it never felt good, so I stopped.

But now, I could tell—I was horny. Fantasizing about being taken by my brother, in his own room.

And so, I gave in to my emotions and started pleasuring myself.

Right there, in his room, not knowing when he might come home.

"You shouldn’t be doing this in Onii-chan’s room! What if he comes back?" my inner angel scolded.

It’d be convenient if he came back now, wouldn’t it? The little devil inside me whispers—Maybe big brother will attack me like in those manga, all excited and everything?

……But if that really happened… what would become of us?

If he pushed his dick inside me, filling me with his seed however he pleased… would I end up pregnant?

If that happened, we could never go back to being normal siblings. Our family would fall apart, we’d lose our place in society, and everyone would be miserable.

I don’t want that. That absolutely cannot happen. But still…

……Just how good would it feel?

Even just touching myself while fantasizing feels this amazing. If big brother’s hands—or his cock—were to mess me up inside, what would even happen to me?

With my left hand, I pick up the tissue soaked with big brother’s desire and press it against my lips.

The dizzyingly strong, masculine scent melts my thoughts away.

"Ahh… Big brother’s cum… smells so lewd…"

I want to get even dirtier.

Driven by instinct, I take the tissue into my mouth.

With obscene, wet sounds, I suck and squeeze out the cum absorbed into the tissue.

A strange sensation spreads in my mouth, making me grimace reflexively.

The nauseating, sticky, raw taste clings stubbornly to my tongue, amplifying the discomfort.

But even that discomfort seems to get twisted into pleasure in my head—teary-eyed, I desperately crave more.

——And so, while thinking of big brother, I reached my first climax.

As the waves of pleasure gradually receded and my mind cleared, exhaustion crashed over my body.

……No.

If I let myself succumb to this fatigue, I’ll fall asleep.

If big brother saw me like this, it’d be a disaster.

In manga, he’d get excited and attack me—but the real him doesn’t see me as a woman at all. He’d reject me as some perverted little sister lusting after her own brother, and we might even lose our sibling relationship entirely.

……Big brother would look down on me if he saw me like this.

The thought terrifies me.

Frantic, I start erasing all traces of what I’d done.

For the next few days, I watched big brother nervously, but he never noticed what I’d done.

After that, I went back to living as usual.

Though occasionally, I’d “borrow” things from big brother’s trash can and lock myself in my room to pleasure myself…

Still, I kept up the façade of a normal little sister, making sure no one would ever discover the feelings growing inside me.

The following year, when I was in my third year of middle school, big brother went missing during his school trip.

It wasn’t until the year after that he finally returned—now a girl.

---

About a year had passed since my brother went missing during his school trip.

Then, one day, he suddenly returned home—in the body of a girl named Alicia.

Apparently, he was on the verge of death in another world when Alicia, using her magic, gave him her body to save him. But her own soul still remained within it, sharing sensations with him.

It was an unbelievable story, but this was the reality my brother had faced.

After that, through various twists and turns, my brother became part of our family as my stepsister, Alice.

Alice—my brother—was unbelievably cute. Yet, despite having once been a boy, she was constantly doing reckless things that made my heart race with worry.

So, I vowed in my heart to become Alice’s big sister and protect her.

My feelings for my brother, who no longer had a place to return to, slowly turned into mere memories. It couldn’t be helped, and I was fine with that.

But then, things got complicated when Alice ended up having sex with our older sister, Hisui.

To help Alicia, who had become emotionally unstable, I somehow ended up having sex with Alice, too.

At that time, urged on by Alicia—who had noticed my feelings—I confessed the love I’d been hiding for my brother.

And my brother… didn’t reject me. She accepted me.

—And now, here we are.

"…So, Onii-chan. Please hold me."

I made an utterly sinful request to my own brother—one that sent shivers down my spine just saying it.

I was about to have sex with my brother.

Though, since she had become Alice, she didn’t have a you-know-what anymore, so I couldn’t give her my first time.

In a way, that was for the best. If I really gave her everything, I might have crossed a point of no return.

If that happened, Mom and Dad would be heartbroken, and we’d have to live the rest of our lives under society’s scorn.

Maybe the only reason my brother accepted me was because, as two girls, it wouldn’t be as unforgivable.

…And honestly, I felt the same.

Alice’s face drew closer, her lips brushing against mine—a soft, fleeting kiss, unlike the deep one from before, signaling the start of everything.

Then, her hands moved to the bath towel wrapped around me… though she was so nervous she was practically trembling.

She’d seen me naked countless times in the bath, so why…? Still, it made me happy that she was really seeing me now.

Clumsily, the towel parted, leaving me completely bare before her.

『Yuna… you’re beautiful. Ikuto-san, say something!』

"Ah… y-you’re beautiful, Yuna."

Urged by Alicia, Alice’s words came out awkward—pathetic, even.

It couldn’t be helped. Since Alicia was still in her body, it felt like we had a chaperone, making things a little uncomfortable.

"Onii-chan, you too. I don’t wanna be the only one naked."

"Got it."

"Ah, wait—I wanna undress you… Just for today, okay?"

Normally, when I tried to undress Alice in the bath, she’d refuse and do it herself.

But today, I had to be the one.

"…Fine."

With a wry smile, Alice gave in. Excited, I moved behind her and began stripping off her clothes.

"Onii-chan, arms up~?"

I bunched up the hem of her dress, sliding it over her raised arms. Obediently, she let me undress her like a doll, leaving her in just a camisole. It felt like playing dress-up, making my heart skip.

Placing my hands on her small shoulders, I traced my fingers along the straps, slipping them down. The camisole fell with a soft rustle.

Beneath it was a familiar pink lace bra. I couldn’t help but peek over her shoulder to confirm.

"Onii-chan, you’re wearing that? The one I picked out for you!"

When I pointed it out, Alice—who had been letting me undress her without protest—suddenly hunched forward, crossing her arms to hide her chest.

"Th-this is… um…"

"I’m so happy! You were thinking about this, huh? Since you always just wear pajamas, I thought I was the only one taking it seriously!"

"…O-of course I was. I mean… I’m doing this with a cute girl like you."

I couldn’t stop the grin spreading across my face.

"Ehehe, I’m so happy… That Onii-chan sees me as a girl… I love you."

"I… I love you too, Yuna."

Our love wasn’t quite the same, but I didn’t ask for more.

"I-I’ll take the rest off myself…!"

Maybe embarrassed by her own words, Alice pushed me onto the bed.

I lay there obediently, waiting for her to finish undressing. I felt like a fish on a chopping block.

"…Sorry for the wait."

Alice, now completely bare, cautiously hovered over me. There was no oppressive weight—her body, Alicia’s, was far smaller than her original one, even more petite than mine.

Her skin was porcelain-white, her silver hair making her look like a work of art. Her small, girlish chest, the delicate pink buds—everything about her was sinfully beautiful.

—And then, between Alice and Alicia, I was pleasured in ways I’d never felt before, experiencing my first climax by someone else’s hands.

---

It was a fluffy, almost weightless sensation, as if floating in the air.

My entire body was enveloped in a blissful feeling, as though something missing had finally been filled. My ragged breathing gradually steadied, and along with it, my rationality returned.

"...Yuna, are you okay?"

In my blurred vision, Alice was looking down at me with concern. It seemed she was worried about me, exhausted and collapsed on the bed after our act.

"I'm fine... thank you, Onii-chan."

I meant to thank her for her concern, but Alice misunderstood it as gratitude for that and turned bright red, stumbling over her words.

"...W-well... you were... really cute. I couldn’t hold back my feelings... I just wanted to ruin you... A-and, I was worried I might’ve gone too far..."

Seeing her like that made me happy.

"You got excited over me? I’m glad, Onii-chan."

...If this was how she reacted, maybe I could’ve seduced her even back when she was still a guy—if I had really tried.

Make her see me as a woman, go on a trip together, spend just one night—then let things spiral from there... Wait, that was Hisui-nee’s tactic.

...But even if I could win her over with emotions, the real problem would come after.

My feelings would only bring misfortune to our precious family.

In that regard, how much had I envied Hisui-nee’s position? She could be with her without causing any problems.

"Are you... regretting it? You look kinda sad..."

Alice asked something completely off the mark.

"There’s no way I’d regret it. I’m happy, really..."

Even if this was just a make-believe substitute.

『Ikuto-san, in times like these, you should just silently hug her.』

"Eh... O-oh..."

Alicia was always so thoughtful and kind.

As I sat up, Alice hesitantly moved to wrap her arms around me. Feeling affectionate toward both of them, I guided her to my chest and embraced her.

Her small, girlish body fit perfectly in my arms. Her hands reached around my back, but it was less of a returned hug and more like she was clinging to me.

"U-um, like this, it feels more like I’m the one being hugged... and your chest is..."

I cradled Alice’s head snugly against my breasts, her warm breath tickling my skin.

『Ikuto-san, you’re disappointing me. Just stay quiet and enjoy this for a while.』

I gave a slight wry smile at Alicia’s bluntness but obediently kept holding Alice.

She really was such a good girl.

『Please think of me as just an extra for Ikuto-san. Like Migratoru’s bird, if you will...』

That was what Alicia had said when we first met.

But after spending our days together, I’d come to see her as something like a slightly airheaded but incredibly capable little sister.

That’s why I wanted to help her in any way I could.

If we could transfer her soul into another body, both Alice and Alicia could be happy.

But revealing the existence of magic to the world wasn’t an option, leaving us with limited means. Searching online only turned up shady, occult-like websites, and even after reaching out to a few, none gave any worthwhile replies.

Hisui-nee was looking into shrine-related leads too, but so far, nothing had turned up.

Our parents weren’t voicing it, but they were also doing everything they could.

...But for now.

The priority was easing Alicia’s worries.

"...Alright then, now it’s your guys’ turn."

The small body in my arms tensed up.

"O-oh right, that was the plan..."

『...Yuna, please.』

Originally, the whole point was to make both of them feel good together.

Alicia, who had been forcibly overwhelmed with pleasure by Hisui-nee, seemed to feel guilty about surrendering herself to someone other than Alice.

But honestly? All the blame lies with Alice.

I mean, even with Hisui-nee—she was the one who walked right into her perfectly laid spiderweb without a care in the world. At that point, it’s practically an invitation.

...Well, regardless of how things got to this point, since Alice was here too, I figured Alicia should be fine enjoying herself with her.

And to confirm that, I was now going to have sex with both of my little sisters.

"For the sake of my adorable little sisters. Big sis will lend you a hand~"

I declared this to Alice and Alicia, my two little sisters.

...Though, considering I’d already been stripped naked earlier, it wasn’t like I had anything left to take off.

Well then—now it was my turn to make them feel good.