Sis, That's Not How You Do It
After that day, a strange new rule took shape between us. It was an unspoken pact, a secret ritual we performed every single night.
Once our parents had retreated to their bedroom and the whole house had sunk into deep sleep, right around midnight, I would slip out of my room like a ghost. Without even thinking about it anymore, I’d walk straight to the end of the hallway and stop in front of my big sister’s door.
During the first few days, my heart would pound like crazy right up until I grabbed the doorknob. But not anymore. Now I felt a strange kind of anticipation, a thrill that made my pulse race for an entirely different reason.
It’ll be unlocked today too.
Confident, I turned the knob. With a soft creak, the door opened without resistance, gliding smoothly. Just as I thought. Unlike before, my big sister’s door was never locked anymore. It was almost like she was waiting for me.
I stepped inside without a sound. Under the faint glow of her bedside lamp, Sis was sitting on the edge of the bed, staring at her smartphone. She obviously knew I’d come in, but she kept pretending to be indifferent, refusing to look up from the screen. It was honestly kind of adorable. Her ears were already burning bright red even though we hadn’t even started yet, and the sight stirred something wicked inside me.
Heh… Perfect. She’s already treating my visits like they’re completely normal.
I cheered silently. Just look at that fake-casual expression. I bet she couldn’t read a single word on that screen. Every nerve in her body was tuned to the sound of me closing the door and walking closer, her heart probably hammering hard enough to burst.
The thought made her seem incredibly cute and hot at the same time. These midnight rendezvous had become our own private ceremony, a natural part of our daily lives.
Sis, who had trembled with fear and shame at the beginning, seemed to be slowly getting used to the situation after a few days. Or more accurately, she had simply given up fighting it.
I sat down beside her on the edge of the bed like it was the most natural thing in the world. The mattress creaked under my weight, tilting slightly. The movement made her shoulder brush against my arm for a brief second before pulling away.
“…”
Without a word, Sis turned off her phone. She glanced at me once, then reached out with a trembling hand that had clearly surrendered to the inevitable. She placed it on my thigh. That was the signal that it had begun.
But even after several days, her touch was still painfully clumsy. Everything was a mess, like someone who had just gotten behind the wheel for the very first time.
Some nights she was so nervous that she gripped me with way too much strength, like she was trying to crush it. I’d have to bite back a scream.
“Ow! That hurts! Sis, you’re not trying to rip it off, are you?!”
“S-sorry…!”
Other nights she went too far in the opposite direction, touching me so lightly it was barely a graze. That was even more frustrating—just enough to tease without any real satisfaction.
“Sis, are you torturing me on purpose? If so, you’re doing a fantastic job.”
“S-sorry…”
I sat next to her like a strict driving instructor, pointing out every flaw in her awkward service.
“You need more snap in your wrist! More snap! How are you supposed to do anything if you’re that stiff?”
“No, that’s not how you use your fingers… That just tickles.”
“Pick up the tempo a little. It’s too slow.”
Every time, Sis would flinch and stammer out another “S-sorry…”, her face growing redder and redder until it looked like a perfectly ripened apple. I found it so lovable that I deliberately teased her even more.
Truthfully, her clumsy touch wasn’t bad at all. In fact, that very clumsiness turned me on even more. The fact that this innocent woman who knew nothing about the world was desperately trying her hardest just for me. The sense of taboo and conquest it gave me was more thrilling than any amount of practiced technique.
But I wasn’t satisfied. A new desire had taken root: I wanted to train her, mold her into the perfect toy that suited my tastes alone.
That day, my shameless lesson continued. I closed my eyes, pretending to savor the pleasure of her touch, then furrowed my brow at the critical moment.
“Ah, not there. That’s too high up…”
When I pointed it out again, her hand froze. Her expression clearly said, Here we go again. She didn’t even apologize anymore; she just bit her lip hard.
I kept complaining. “I told you, that’s not how you use your fingers. Wrap your second and third fingers around the shaft like this…”
My detailed instructions made her face burn even brighter. She was completely shrinking under the constant criticism.
But today, something was different.
She paused her hand for a moment, then looked up at me with what seemed like a huge decision already made. Under the lamplight, her dark eyes sparkled more than usual. Her face was flushed scarlet, but there was a new seriousness in her gaze that hadn’t been there before.
In a small but clear voice, she asked, “L-like this… is it okay…?”
She was gripping me a little lower than the spot I had rejected earlier, using a slightly different technique that was entirely her own. The mechanical girl who had only followed my programmed instructions had suddenly asked a question like an AI developing self-awareness.
I stopped breathing for a second. An unexpected question. I had assumed she was just waiting for this time to be over as quickly as possible, but here she was, asking how to make it better.
That simple question hit me with a powerful shock that went beyond mere physical pleasure, like my heart had dropped straight through my chest.
…This is insane.
This… this is totally unfair.
I stared at her blankly. Sis kept looking up at me with those serious eyes, waiting for my answer. Her gaze seemed to beg, Please tell me it’s right.
In that moment, I realized how stupid I had been.
I had thought of this whole thing as my personal pleasure, my personal conquest. I had seen Sis as nothing more than a passive receptacle for my desires. But that wasn’t true at all.
This girl was trying so hard to make me feel good. She was clumsy, but she was putting in real effort in her own way. For me.
That realization stirred up emotions I had never felt before. It wasn’t just lust or possessiveness. It was a tender ache in my chest, gratitude, and… something else. An overwhelming surge of feeling I couldn’t even name.
Before I knew it, I answered in the softest voice I had ever heard myself use.
“…Yeah. That’s perfect, Sis. It feels… really good.”
“R-really?”
At my praise, her face seemed to bloom. Of course she was still bright red, but her expression now held clear relief and a tiny spark of joy. Her touch became much more confident and gentle than before. She even started adjusting the pressure on her own, exploring what I liked without me having to tell her.
That night, I experienced a level of pleasure that was completely different from anything before. It was a satisfaction that shook me to my soul, combining physical ecstasy with genuine emotional connection.
When it was all over, a brief silence filled the room. Normally I would have cleaned up and left immediately. But today, I didn’t want to.
After hesitating for a moment, I impulsively reached out and gently stroked her hair. It was a little greasy since she hadn’t washed it in a few days, but that didn’t matter at all.
“…You did well, Sis.”
Her shoulders stiffened. I quickly pulled my hand back and practically fled the room, like something was chasing me.
Back in my own room, I flopped down onto the bed. My heart was still racing like crazy. I could still feel the texture of her hair against my palm.
Shit… Something’s gone seriously wrong here.
Until now, Sis had been like a walking R-18 doujinshi to me. Just looking at her got me hard; she was a target of pure primal lust that I wanted to experience at least once. But now?
…Why does she seem so cute?
That serious expression from earlier, the way she got flustered by a single word of praise, how her shoulders had flinched when I patted her head… I couldn’t get any of it out of my mind.
Yes, legally we were unrelated. We were step-siblings with zero blood in common. If we wanted to, we could even get legally married. But from a societal perspective? This was completely out of bounds. It was an undeniable realm of taboo.
What if our parents found out? Dad would probably clutch his chest and collapse. As for my stepmom… I didn’t even want to imagine it. Our family would be destroyed in no time.
My brain knew this. It was crazy. It was dangerous playing with fire. My reason was blaring warning sirens, telling me to stop immediately.
But… fuck.
I couldn’t stop thinking about those dark eyes looking up at me. That small voice asking, “Like this… is it okay?” The way her face had filled with embarrassed joy like she’d been given the whole world when I praised her. And those small, soft hands desperately working to please me.
My head was screaming to stop, but my heart and my dick were both shouting full speed ahead.
Damn it… So it wasn’t just because she turned me on…
That night, I couldn’t fall asleep until late into the early morning.