My stepsisters are sexy demons, and I must protect them
Chapter 55: Unity is strength!

Chapter 55: Unity is strength!

«Miss... Yuzu Kurotsuki...?» the courier murmurs.

He’s barely holding a big and heavy package.

«Here I am!» Yuzu exclaims, over the moon. She knows exactly what’s inside that box.

She grabs it without hesitation, rips it from his hands, and lifts it as if it weighs nothing.

«Bye bye, good work!» she says, then shuts the door with clear impatience.

Rika watches her, clearly confused.

«Yuzu... what the heck is this...?» she asks.

«Don’t you remember what I told you just yesterday? About my amazing plan? The one where you and I could become as good as Mom at making Hakuto feel pleasure? Well...»

Yuzu’s eyes sparkle.

«My brilliant plan has finally arrived!»

«I’m afraid to ask what’s inside...» Rika murmurs.

«You’ll find out right away! Come with me!»

They head upstairs to the second floor and lock themselves in their bedroom.

The big box sits on the bed.

Yuzu trembles with impatience, while Rika watches with simple curiosity.

She has no idea what her sister’s twisted mind might have come up with.

...and when Yuzu unwraps the package...

«Y-Yuzu... what the heck is this...?» Rika asks, her face red with embarrassment.

Lying on the bed is an inflatable doll – a sex toy that mimics Hakuto’s features with unsettling precision.

EVERY feature of Hakuto has been reproduced down to the smallest detail. Even that one, which stands upright.

«Don’t you get it yourself...?» Yuzu asks, confused.

«Y-Yes, I got it... but why?!»

«This isn’t just some inflatable doll! It’s a jewel of technology!» Yuzu exclaims, visibly more excited.

«It doesn’t just replicate the skin using super realistic synthetic fabric... it’s also equipped with advanced AI! With cameras and sensors all over its body, it can capture touch, sight, and sound... and turn them into human-like reactions!»

Yuzu doesn’t understand a single word of what she just said.

She’s just parroting what the company told her when she ordered it.

Rika, on the other hand, is a real genius.

She knows exactly what all of that means.

«...to keep it simple, this thing can evaluate and correct our sexual performances! It tells us how good—or how bad—we are... what to do, what to say, everything to boost our skills! It cost me a fortune... almost all my savings... but to make my big brother happy, I’d do even more!» Yuzu concludes, completely euphoric.

«I think this is the worst money you’ve ever spent in your life...» Rika says, shaking her head.

«What? Weren’t you the one who got jealous because Hakuto liked Mom more than us? And now that I’m giving you a way to reach her level, you treat me like this...?»

Meanwhile, Yuzu pulls down her shorts and panties.

She lets them drop to the floor and stays in just a long tank top, no bra underneath.

«...don’t be mad when big brother starts preferring me over Mom and you!»

Then, Yuzu climbs onto the bed.

She gets on her knees, right over the huge rubber dick sticking out of the doll.

«...It’s time to put this gadget to the test!»

Then, Yuzu slowly lowers her hips.

The dildo slides into her pussy.

Moans escape her lips right away—high-pitched, almost exaggerated, like she wants to make her sister jealous.

She starts to move her hips, faster and faster.

Her hands grip the doll’s hips tightly.

Her breasts bounce in sync with the rhythm.

«Little sis, put your hands on my chest.»

The inflatable doll speaks in a youthful, masculine voice.

But it sounds nothing like Hakuto.

«Why is he calling you little sis..?» Rika asks.

«I-It’s part... aaah... part of the instructions I gave him... aaah...» Yuzu replies, panting.

«He can recognize both of us... C-Come on, big sis... come here!»

«W-What am I supposed to do...?» Rika mutters, clearly embarrassed.

She wouldn’t normally feel this way if the one lying on the bed was the real Hakuto—her Soulmate.

But this isn’t Hakuto.

It’s just a sex toy that looks like him.

Still, Rika hesitates.

And slowly, she starts to undress.

She takes off her shorts and panties and lets them fall next to Yuzu’s clothes.

Rika gasps as soon as her pussy touches the doll’s face.

Something just moved.

A tongue.

Not a real one—but soft, rubbery, and coated in a warm, slippery liquid that mimics the real thing.

Without thinking, Rika leans forward.

Her hands press against the mattress.

The tongue slides inside her and starts to lick with precision.

Planned, mechanical precision.

Rika gasps and moans.

Her cheeks turn red, but not from embarrassment anymore.

«W-What did I tell you, big sis...? Aaah... this is the best money I’ve ever spent... aaah...» Yuzu says between breaths.

Her voice is trembling.

She keeps bouncing on the rubber cock, soaked in her fluids, which drip down onto the mattress.

«H-Hakuto...» Rika murmurs.

The idea of talking to this thing like it’s a real person is too much.

«W-What should I do...?»

The doll stays silent.

Ten full seconds pass.

Then, it speaks.

«Sit on my face, my beloved sister.»

Rika swallows.

«W-What are you waiting for, big sis...?Aaah... move or she’ll get angry... aaah...» Yuzu moans.

«This is the most embarrassing thing I’ve ever done in my life...» Rika mutters.

But she still moves.

She takes off her shorts and panties and lets them fall next to Yuzu’s.

Then, slowly, she sits down.

«Rika, undress your little sister.»

Once again, the sex toy gives instructions.

Its voice sounds a bit more involved than before—like it’s trying to mimic the rising arousal a real boy would feel.

Rika doesn’t hesitate.

She grabs the edge of Yuzu’s tank top and yanks it upward.

In one swift motion, she exposes Yuzu’s huge, bare tits.

«Now, lick her nipples.»

Rika freezes.

She stares in shock, completely thrown off by the command.

«W-What...? Why would I do something like that...?!»

«B-Big sis... don’t argue... aaah... this thing was programmed to turn us into sex machines... j-just do what it says...» Yuzu scolds her between moans.

Her voice is trembling with pleasure.

Rika hesitates for a moment.

She’s still confused, a bit disturbed.

But eventually, she gives in to Yuzu’s insistence.

She leans forward.

Her lips hover just a breath away from her little sister’s perky nipples.

And then...

She starts to lick.

«B-Big sis... I didn’t know you were that good... H-Hakuto taught you how to lick really well... aaah...»

Yuzu trembles in pleasure.

Rika squeezes her breasts, licking and circling her tongue around the nipples.

She sucks gently, then nibbles, then licks again.

Her saliva glistens on Yuzu’s tits.

The mannequin starts to moan too.

Its voice is awkward, mechanical—like a looping audio file.

«Now it’s your turn, little sis, to lick Rika’s breasts.»

«A-Yes, boss... aaah...»

Yuzu doesn’t hesitate for a second.

She grabs Rika’s tank top and pulls it off in one motion.

Then she lunges at her sister’s modest, firm breasts like a starving beast.

No delicacy.

She licks them roughly, with chaotic energy—like a washing machine on full spin.

It’s completely different from Rika’s style.

But the result is the same.

Rika’s moans are loud.

Too loud.

She keeps her mouth shut, trying to hold them in.

The mannequin’s tongue moves inside her soaked pussy.

Yuzu’s tongue attacks her breasts.

The pleasure is overwhelming.

Rika’s whole body shakes from head to toe.

«I-I’m cumming, Yuzu... I’m gonna cum...» she gasps.

Her hands dig into her little sister’s thighs.

«M-Me too, big sis... me too...»

«Aaaaaah...»

Their voices blend into one long moan.

They collapse forward—exhausted, trembling, drenched.

Their juices drip onto the mannequin’s face.

«B-Big sis... say again this was the worst money I ever spent, if you dare...» Yuzu pants, completely out of breath, her face glowing with ecstasy.

«M-Maybe... maybe I was wrong...» Rika responds softly.

She’s not the type to admit her mistakes easily.

But deep down, she might be even happier than Yuzu about that absurd purchase.

The mannequin’s voice cuts through the moment.

A few loud BEEP BEEPs follow.

«Sexual performance analysis in progress... Sexual performance analysis in progress...»

In just a few seconds, the internal software completes its process.

The results appear, complete with a score from 1 to 100 and a short technical commentary.

Rika’s individual rating: 53 out of 100.

You lack initiative and imagination.

Having a nice body helps, but if there’s nothing else beyond that, your partner could quickly get bored.

Yuzu’s individual rating: 61 out of 100.

You show more creativity, but your technique is still very basic—a clear sign of inexperience.

Even in your case, your partner might lose interest quickly.

Overall relationship rating: 72 out of 100.

Despite your mediocre individual scores, the interaction between the two of you greatly boosted the final result.

The fact that you’re sisters gives a strong bonus—according to my data, 89% of men fantasize about threesomes with sisters.

«Fifty-three out of a hundred... ugh... I really am a disaster...» Rika mutters, clearly shaken by the brutal score.

«What should I say...? I gave it everything I had. More effort, more enthusiasm... and I only got eight points more than you...» Yuzu sighs, equally frustrated.

«I’d be curious to see what score Mom would get... but I have the feeling that if she tried, our self-esteem would hit rock bottom.»

Suddenly, Rika’s eyes widen.

She’s had an epiphany.

«You heard what that thing said, right...? We suck alone. But together...»

«Of course! You’re a genius, big sis!» Yuzu lights up again, full of energy.

«Mom might be way better than us, but we’re two! We’ll use our numbers to our advantage!»

The two sisters exchange a determined look.

«We’ll keep going... until we get a duo score of at least ninety!»

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