Through the Narrow Gap
"......"
Holding a silenced pistol, Moi patrolled silently around the temporary outpost like a stealthy cat.
The long years of wandering had taught her how to survive in the darkness.
With all her senses on high alert, she braced for any threat to herself, her sister, and everyone in the outpost.
[Grk, grrr....]
At that moment, a staggering figure approached from the shadows.
Zombie... a low-grade one.
A starving low-level zombie, too blinded by hunger to even watch its surroundings.
Moi watched it from behind a pile of concrete debris, her expression unchanging.
To survive as a Wanderer, she had to dispatch pests like this with ease.
No need for the gun.
Moi holstered the pistol—which could still make some noise—and drew her combat dagger instead.
It was a razor-sharp titanium-alloy military knife that the new Commander had issued to her.
The grip and weight felt unfamiliar yet reassuring.
Melting completely into the shadows, Moi sprang out like a coiled spring the instant the zombie shuffled past without noticing her.
Without hesitation, she plunged the blade into the back of its skull and twisted.
Splat!
With a chilling sound, the zombie collapsed into a limp heap of meat without a single cry.
"......"
Moi pulled the dagger from the corpse, wiped the blood on its filthy clothes, and quickly scanned the surroundings.
She had to check if the faint noise had drawn any others.
Just then, Rai's voice came through her communicator.
[Sis, you okay?]
"You noticed?"
[Yeah. Saw it all from up here.]
Moi looked up to see Rai scanning the area with a pair of binoculars from the rooftop.
"Any other hostiles?"
[Um... doesn't look like it from what I can see.]
"Got it. Heading back."
Returning to base, Moi gave the outpost entrance one final thorough check before climbing the stairs inside.
Rai had already come down from the roof and settled near a window.
Moi sat beside her sister and pulled out a concentrated nutrient bar.
A hearty return meal packed with energy—a rarity on the surface world.
That's when Rai spoke up abruptly.
"We'll be heading to the Ark soon too, right?"
"...Why? Don’t wanna?"
Moi glanced toward the inner room where the Commander was.
Honestly, she didn't mind this Commander at all.
He was kind to the ECHOs and made sure they never went hungry.
Just looking at the other ECHOs following him told her everything.
This Commander was a good man.
All the ECHOs she'd seen before had indelible shadows under their eyes, but these were different.
They brimmed with life, like they were truly alive.
Which made the young Commander stand out from any human she'd encountered before.
But even so, if her sister Rai disliked him, Moi was ready to leave and return to wandering at a moment's notice.
Rai was everything to her.
"Nah."
Rai shook her head while peering through the binoculars.
"This Commander's... really nice, somehow. Feels like it'd be okay to join a new Ark."
"He is unusual. Treating ECHOs this well."
Moi shook her nutrient bar for emphasis.
That said, she wasn't following him 100% wholeheartedly yet.
The scars from years of wandering and human cruelty didn't heal that easily.
"Yeah. Doesn't seem like he wants to hurt us, at least."
"Right?"
Moi nodded quietly at her sister's words.
That was why.
She didn't fully trust him yet, but there was that minimum faith—that he would never harm them.
Because of it, she followed orders like night watch without complaint.
She was about to refocus on guard duty when—
[...Nggh, aaah! Aaaaaaaauuu—!]
A faint but unmistakable sound.
Moi and Rai froze instantly.
It wasn't a battle cry, but a muffled feminine moan.
Their heads snapped toward the source— the Commander's room.
"Saw Sister Pomen go in earlier..."
"Yeah..."
"Doing that again?"
Moi's face flushed at Rai's words.
It wasn't the first time they'd heard those noises.
[Haah! Uh! Aaa—! C-Commander! More, moremoremoremore! Thrust harder—! Thrust it...! Uhng! Aaaang!!!]
Pomen's ecstasy-drenched screams faintly pierced the sisters' ears.
Unable to resist her curiosity any longer, Moi moved first.
She crept silently, and Rai followed, drawn by some inexplicable pull.
Like the most stealthy cats, the sisters padded to the door where the sounds leaked out.
The thick steel door had a small gap from years of wear—perfect for their peeping.
"Hngh! Yes! Ah—!! Aaaah!!! C-Commander!!!"
"Hah! Hah!"
"More, more—! Aaaah!!!"
Through the crack, Pomen was on all fours like a beast, taking the Commander's cock.
Each time he thrust with ragged breaths, her breasts jiggled wildly, filling the room with lewd moans.
And she cried out with an ecstatic expression like she owned the world.
"That's..."
"Told you before, right? Sex. That’s what humans do together."
"H-Humans do that?"
"Yeah. They have sex like that to..."
Moi was about to explain with knowledge picked up during her wanderings when—
"Ughng! Uh! Uh! Oh! Ooooh!!!"
A piercing scream erupted from Pomen like a beast's roar.
With it, thick white semen gushed into her through the hole between her legs.
So much that it overflowed her pussy and streamed down her thighs.
"...make babies. That white semen goes inside a woman and makes a child."
"Ah.... But Sister Pomen is an ECHO, though?"
"Usually, yeah... but I heard humans do it for pleasure too."
"Pleasure?"
Moi scratched her head at Rai's innocent question.
How to explain physiological pleasure—a complex mix of physical, psychological factors, neural transmitters, and hormonal responses—to her young sister?
But then a better idea struck.
One experience beat a hundred words.
"Sis...? Hn?!"
"Shh. Gotta be quiet."
"Uh, u-uh-huh."
Moi activated Rai's sensory sync device and gently caressed her sister's slit with a finger.
Tracing the parted folds in soft circles, a thin moan escaped Rai unbidden.
"Hngh—! S-Sis...! F-F-Feeeels... weeeeeeird...!"
"Feeling that tingle in your lower belly, right? Focus on that feeling."
"Ah, aaah.... Uh!"
"Sshhh! We can't make noise. The Commander'll hear."
"Mmph! Mmmph!"
Rai clamped her hand over her mouth at her sister's warning.
Undeterred, Moi kept stroking her sister's pussy.
Recalling the Commander's motions through the crack, she boldly stirred the slick folds and relentlessly rubbed the sensitive nub.
"Mmph! Mmng! Hnngh! S-Sis... wait...!"
Rai's legs buckled, and she slumped to the floor.
And then she looked down with dazed eyes.
The ground was soaked, wetness trickling from somewhere.
"Ah!"
Was this pleasure?
An intense, dizzying stimulation.
Meanwhile, the Commander and Pomen went at it again fiercely.
Sloppy tongues intertwined, sounds of groping and sucking voluptuous breasts with ravenous hunger.
After indulging in each other's bodies, they overlapped once more.
"A-Ah—! Commander!!! D-Do you like me? Does my body taste good—?!"
"Of course. That's why you're...!"
"Uh! Uuung! A-Anytime! C-Call me whenever! I'll pre-prepare my pussy for you to use every day—!"
Their sex went on for quite a while longer.
Moi and Rai, who had watched the whole time, scurried back to their guard posts when the Commander stirred.
Fortunately, no zombies in sight.
Moments later, the Commander's door opened. Pomen emerged drenched in sweat, the Commander with tousled hair.
The thick, musky scent in the air flushed the sisters' faces again.
"...Found anything during guard duty?"
"N-No issues really."
"Yes. One lost zombie approached, but I handled it."
"You did? Good work, Moi."
The Commander praised her, stroking her head. Moi swallowed hard at the novel sensation.
"Go rest inside now. Pomen and I'll take over."
"...Yes, Commander."
The sisters bowed hastily and fled to their assigned small room.
The door barely shut before they faced each other, as if by agreement.
The forbidden scene they'd spied on.
And the unknown pleasure they'd felt for the first time.
It filled the air with awkward heat.
Rai grabbed her sister's hem with trembling hands first.
"Sis... th-that thing from before... one more time..."
"Can you stay quiet?"
"Uh, y-yeah.... I'll try."
Moi wordlessly pulled her sister into her embrace as she nodded frantically.
Feeling each other's cores, Moi groped her sister's body.
This time, Rai joined in.
She clumsily caressed her sister's softest place, mirroring what had been done to her.
"Hngh—!"
"H-How is it?"
"There's... a slit here? Feels good there."
"Y-Yeah."
"Don't go too hard or it hurts. Be gentle."
"Ah! S-Sorry, sis."
They clung tightly, legs entwined, rubbing their bodies together.
Even through rough combat suits, the friction sent dizzying sensations straight to their cores.
"Haahng! Uh!"
"S-Sis.... Uung!"
Body heat, breaths, and pleasure-laced whimpers filled the room.
"Rai..."
"Sis... smack! Mmmwah!"
They didn't know how to undress or probe deeper.
Guided by instinct, they shared tongues, ground bodies, pressed sensitive spots together, and rocked.
But it was enough.
"Huuung! Uh!"
"A-Ahang!"
The fiercer the friction, the more uncontrollable the pleasure swelled inside their bodies and minds.
A thunderous climax crashed over them together. They clung to each other, trembling faintly in the safety of their shared embrace.
Soon after, in the afterglow, the sisters leaned into each other and drifted into sweet, languid sleep.
But the new sensation was too intense.
Deep in the night, Rai woke up from the heat enveloping her entire body.
"...Sis?"
"......"
"...She's asleep."
She wished her sister would touch her again.
Rai quietly slipped back to her sleeping bag and cautiously slid a hand between her legs.
She began exploring that unknown pleasure alone, as she'd felt with her sister.