Lying on the carpet with my younger sister straddling me, I gripped my exposed penis in my hand.
Despite the bizarre situation, my cock was surprisingly hot and hard.
I had no hesitation. Paying no mind to the fact that she was watching so closely, I began stroking it vigorously with my right hand.
"Wow, so that's how you do it..." Matsuri observed with keen interest, watching my hand move up and down.
Well, well, she sure seems to love penises. This little bitch.
Come to think of it, during Miki's last session, Matsuri had been staring intently at my penis the whole time.
"Wait, though... this feels different from last time..."
At first, I didn't understand what she meant by "different," but I realized she must be referring to the state of my penis.
My penis was fully covered with its foreskin now. Come to think of it, Matsuri had only ever seen my completely bare penis before.
"Hey, it's not the same, right?"
Even when she said it with such bewilderment...
I mean, I know the difference between a foreskin-covered penis and one that's fully exposed.
Well, even I was astonished the first time I saw a completely bare erect penis.
Matsuri, on the other hand, must be used to seeing her boyfriend's penis, right? So does this mean... she's demanding I strip it off and start masturbating?
"N-no, well, if I take it off, it's still pretty complicated..."
"Compli-cated? This is supposed to be easy?"
Having plenty of experience masturbating with my foreskin, I can go from full erection to orgasm in under a minute.
But I have no intention of doing a sloppy public masturbation while my younger sister is watching.
From the start, I'm on the fast-track to orgasm, vigorously sliding the foreskin up and down over my glans.
"The tip's bobbing up and down... Peeking out, hiding, so naughty~"
I thought the thrill of excitement had banished my shame, but having her commentate like this makes it incredibly awkward.
Even so, the stimulation to my penis since Miki had last played with it was rapidly pushing me toward climax.
"Hey, aren't you embarrassed? Having someone else watch you touch yourself?"
Damn it... I was just about to ride that wave to orgasm, but her words threw some kind of weird brake on everything.
Matsuri's triumphant smile only intensified the indescribable humiliation, making me suddenly want to snap back to reality.
What is this little sister even thinking...?
Just then, Matsuri's hips shifted restlessly on my thigh.
I could feel her body heat through the soft contact. Suddenly, it began to grow intensely warm.
Could she actually be getting aroused?
Matsuri's slight, jerky movements were strangely provocative. The renewed arousal pushed the lingering shame back into the corners of my mind.
Without answering her question, I let out a rough breath and resumed stroking my penis with renewed vigor.
It's almost there. Just a little more...
"Wait a minute."
Just as I was about to climax, a hand clamped down on my wrist from above.
I had no choice but to stop moving my hand up and down.
"W-what?"
"You were moving too fast, trying to finish quickly and be done with it, weren't you?"
"Huh? That's..."
That's true, but is there a problem with that?
"Slow down."
"S-slow down?"
"Yes, slow down. It's an order."
An order? Seriously? Who gives such detailed orders...?
It's really frustrating to be stopped just when you're about to orgasm. I was already completely ready to come.
Reluctantly, I slowed my strokes and resumed masturbating.
Since I was already so close to climaxing, even the sluggish movements were enough. They didn't actually tell me to come, after all.
Either way, I felt like I was about to explode. My cock was practically begging to release.
"Don't just let it spill on its own, though."
Ugh! My hand froze.
If she'd said anything a few seconds later, I would have already come.
"...You were about to climax just now, weren't you? You're too fast anyway. Slow down."
"What? What do you mean by 'slow down'? How slow?"
"Huh? Umm..."
Matsuri furrowed her brow, deep in thought.
I didn't know what she was pondering at that moment, but I had a bad feeling.
Eventually, as if struck by an idea, she pointed at my hand, which was gripping her penis, and spoke.
"...That... the moving of that... that's called 'jerking,' right?"
"Hmm? Well, yeah..."
"Okay, so move your hand at the speed I tell you to."
For a moment, I was confused, wondering what she meant.
"Come on, jerk, jerk, jerk..."
But I quickly understood her intention.
Following Matsuri's instructions, I slowly moved my hand in rhythm with her voice.
At this pace, it might work... or it might not.
"Shiko, shiko... Hehe, this is so funny. You're actually moving exactly as I tell you to."
"N-no, you're the one telling me to move..."
"Hey, if you stop, that's 'stop'!"
Ugh, what kind of weird game is this?
Despite my thoughts, I continued to obey Matsuri's commands.
"Right, right, stop... Now let's go? Shiko, shiko..."
Once again, I slowly began moving my hand.
My younger sister, telling me to "shiko, shiko" while I jerk off.
This is going to be some seriously messed-up black history.
But as I continued, for some reason, I started getting aroused.
Matsuri, relentlessly repeating "shiko, shiko" and uttering obscene words. In this case, she's probably the one who should be embarrassed.
Matsuri is acting really strange today. I have no idea what she's up to...
"Heh, heh-heh..."
Suddenly, Matsuri bursts out laughing in a creepy way.
When I glance up at her face, she's wearing a look of absolute glee, as if she's having the time of her life.
It's almost like she's high on some dangerous drug or something.
"Wh-what's wrong with you? That's gross..."
"What? You're just my little puppet, so don't you dare talk back to me!"
This girl is a true sadist at heart.
But since she's basically low-grade, she probably can't actually dominate anyone unless she's in a special situation like this.
And she's so damn happy about it? How pathetic.
"You just got into some decent school, and you're getting all full of yourself, aren't you? Just a fluke, if you ask me."
Ah, so that's been bothering her all along.
I figured she was just jealous because I got into such a good school.
Meanwhile, I failed my entrance exams and got chewed out for it.
Honestly, what a pathetic—no, what a poor little sister.
"You just need to listen to me and do as I say, like you used to."
Sure, when we were younger, I played along with Matsuri's games, indulged her whims... but frankly, none of that matters to me anymore.
Right now, I just want this damn penis, which is about to explode but can't, to stop hurting so much.
"Got it?"
"Yeah, yeah, I got it."
Who are you talking to, idiot? Go talk to yourself.
Just hurry up and continue—keep stroking it already.
"Really?"
"Sure, really," I agreed casually.
Matsuri smiled contentedly, her voice taking on a smug tone. "Well then, I'll start fucking you, big brother."
Her sudden saccharine voice was creepy, but I figured it was just another one of her weird acts and let it slide.
I gripped my pre-cum-slick penis, waiting impatiently.
"Come on, fucking, fucking..."
I pumped my fist vigorously up and down in rhythm with her fucking chant.
Maybe it was just my imagination, but her voice seemed more emotional than before. It was just the same words, but somehow I found myself getting unusually aroused.
"Fucking, fucking, fucking..."
This time, the pace quickened.
Naturally, my hand sped up to match.
"Fucking, fucking... Hey, does that feel good?"
"U-um, yeah."
"Shikoshi... it sounds kinda ecchi. Does it turn you on?"
"Yeah."
I was so focused on stroking my penis that I could only manage one-word answers.
Matsuri's unusually gentle voice, which I'd been wary of at first, was gradually becoming comforting.
"Shikoshi... shikoshi... how's it feel? About to come?"
When she asked if I was about to come, the truth was, the urge to ejaculate was building.
In fact, I was already at my limit.
This must mean she's okay with me coming.
"Shikoshi... okay, stop!"
Stop again? I can't take it anymore. I can't keep playing along.
Having reached my limit with the teasing, I ignored her and kept stroking.
"Ah! I told you, stop it!"
Matsuri frantically tried to stop my hand, but I couldn't stop moving.
"Ah! Oh, you're going to...!"
"Wait, no, seriously?!"
"T-tissues..."
I hastily grabbed three or four tissues from the box lying nearby.
Holding the tissues in my left hand, I covered the tip of my penis and prepared to ejaculate.
"Ah, no, you can't do that!"
"Huh?"
"I want to see the moment it spurts out."
"S-see it...? It'll get messy."
"Just wipe it off later."
But if it gets on my clothes...
As I fumbled, Matsuri snatched the tissues from my hand, spread them wide with both hands, and positioned them just above my navel.
"Okay, I'll hold the tissues open for you. Just aim and shoot."
I thought, If we're using tissues either way, what's the difference? But Matsuri insisted on witnessing the exact moment the semen erupted.
I hope it lands well, but the trajectory of the sperm is entirely up to my penis.
Still, she wants to see where it comes out... Ugh, she always manages to say something unsettling.
As I hesitate slightly,
"What's wrong? You want to come, don't you? Go ahead, let it out! Come on, stroke, stroke, stroke..."
My hand moves reflexively, as if I've been enchanted by some spell.
My penis, already on the brink of climax, instantly enters a countdown to explosion.
"So, will it fly? Will it spray everywhere?"
"I-I don't know..."
"You don't know? Even though you're the one letting it out?"
Matsuri's incessant chatter distracts me again.
So it all depends on my dick.
I don't know if he's thinking of it like peeing, but does he really think he can control how much he ejaculates?
"Tell me when you're about to come. If you don't—"
"Ah! I'm coming!"
Matsuri was about to say something when a powerful stream of white fluid shot out from the glans.
Just as Matsuri had hoped, the first jet made an unexpected trajectory, splattering onto the tissues she held in her outstretched fingers.
"Whoa!"
Dok, dok, dok...
Then, a thick, jelly-like white liquid began spurting rhythmically onto the tissues.
Perhaps due to the repeated teasing earlier, the volume was unusually high. The tissues she had prepared quickly turned into a sticky mess.
"Wow, that's so much..."
Matsuri abruptly tossed a semen-stained tissue onto my stomach (hey, what's this?) and brought her finger, still coated with semen, up to her face.
She began to play with it between her fingers, cautiously bringing it closer to her nose, sniffing to confirm the scent.
Meanwhile, she unconsciously fidgeted, rubbing her thighs as she wriggled her body.
From the places where our bodies had touched, a wave of heat, intensified by our earlier intimacy, radiated toward me.
Still lost in the lingering afterglow of pleasure, I watched her. Suddenly, Matsuri noticed my gaze.
"Ah! This... I'm going to wash it off!"
She hastily stood up, straddled my prone body, and left the room.
After that, Matsuri didn't return for a long time.
When she finally came back, she barely spoke, silently gathered her underwear and notebooks, and fled the room.