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Unclassified Cohabitation

Summary:

In a hidden research facility where halfkinds- part human, part animal- are studied under the guise of humane care, Vesper, a sharp-eyed feline, lives a quiet, solitary life. She keeps to herself, compliant but emotionally distant, until she begins to suspect something is sharing her space.

Something small. Something clever.

Chapter 1: Sounds in the Walls

Summary:

Vesper knows something- or someone- is in the walls. She's not afraid, just interested. She starts testing the presence, coaxing it out- not to threaten, but to play her part in this little game.

Chapter Text

Vesper lived in a home designed exactly for her– tiered ledges to perch upon with room for her tail to hang, nail files embedded in the walls for maintaining her claws, an endless source of warmth from the heater. It was a near perfect environment for her kind. It was quiet, comfortable, and always just a little too clean.

The walls were a pale oak veneer, warm and soundproofed. The lights adjusted automatically to her circadian rhythm. The mattress molded to the curve of her spine. The food was nutritious, varied, and brought daily by a staff member who smiled just enough to seem human but not enough to be memorable.

Everything was accounted for. Everything was balanced. And everything felt… staged.

But Vesper had learned not to complain. Life here was leagues better than the alternatives.

Six years ago, she’d been pulled out of a holding cell in a crumbling municipal building– the kind of place the outside world used to dump halfkinds they didn’t understand or want to deal with. Back then, she'd been nearly feral, 17, covered in bruises, and ready to scratch anyone who got close.

Now, at 23, she lived in a secure facility hidden somewhere far from cities or towns. She still didn’t know exactly where it was. She was just picked up and taken here one day- a kind of crisis intervention, she was told.

There had been no road signs. No maps. Not even a glimpse from a window that faced beyond the perimeter. The courtyard she was permitted to visit had tall walls made of stone and green growth– ivy, moss, creeping vines– all lovingly maintained. But she'd never been allowed to touch the gate.

Still, her room wasn’t a cage. It had real wooden floors and soft rugs. Shelves filled with books. A small screen where she could request certain programs: documentaries, educational courses, the occasional fiction.

She even had a door she could lock– from the inside.

But freedom was measured in permissions, not rights. There were rules. She was expected to check in each morning via her wristband. She had to attend medical evaluations once a week and could be summoned at any time for non-invasive testing. She was free to refuse certain things. Not everything. But enough to feel like she still had some say in her own body.

Enough to play along.

Vesper was human enough to walk upright, speak fluently, and pass at a glance in poor lighting. But her feline traits were impossible to hide. Large fluffy ears sprouted from the side of her head, often flicking at sounds no one else could hear. Her pupils shifted from round to slits in bright light. Her yellow eyes reflected light at night. Her nails could lengthen into claws when she was threatened– or irritated. Her tail twitched and curled unconsciously, a dead giveaway of mood.

Her senses were absurdly sharp. She could hear a moth crawling along the ceiling. See clearly in pitch black. Scent tracks.

And lately, she'd been sensing something she wasn’t supposed to.

It started three nights ago.

She was drying off after a hot shower, standing barefoot in the mirror. Her routine was predictable, something she found calming. She liked the smell of her conditioner. She liked the feel of the brush in her short hair, the steam still heavy in the air.

Then, a scrape.

She stopped mid-stroke. Her ears twitched sharply toward the sound– somewhere above the closet. A vent.

She stood motionless for several seconds, listening. The silence that followed was too perfect.

Eventually, she dismissed it. Could’ve been a shift in the duct metal. Could’ve been her own imagination. She went to bed.

But the next night, it came again.

This time, it was quicker– like a series of tiny footfalls moving through the ventwork. A burst of soft noise, then silence.

She waited in the dark, stretched out in bed, listening.

Nothing.

The morning after that, she noticed the teaspoon missing.

She wasn’t obsessive, but she knew her kitchen. She liked things in their place. Everything had an order. And one of the small silver spoons, the one with the slight bend in the handle, was simply gone.

No knock. No maintenance visit. No drone. No explanation.

Vesper stood in front of the drawer for a full minute, just breathing slowly through her nose, trying to decide if this was something to mention.

She didn’t.

By the third night, the sounds had a pattern. Always late. Always brief. Always just when she wasn’t expecting them.

Skitter. Click. Scrape. Pause.

Like something– or someone– was exploring. Testing boundaries.

She didn’t report it. That was instinct. The facility staff, though cordial and well-trained, had a habit of reacting to anomalies with... over-correction. She’d seen it before. A halfkind with bird traits had once reported strange lights flickering in his room. The next day, he was relocated out of the wing.

So instead, she waited.

That night, Vesper curled up sideways on the couch, book in hand. Bacterial Symbiosis in Post-Natal Mutation Events. Dry as hell, but she liked understanding the science of what she was.

She read, eyes scanning pages rapidly, but her ears were fully alert.

And there it was again.

A soft, almost shy rustle from behind the vent near the corner bookshelf. A tap. Something brushed the metal.

This time she didn’t look up. She turned a page. Slowly. Calmly. Silent.

She could feel it. Something behind the wall was listening too.

After another long moment, she shut the book gently and spoke.

“…I know you’re there.”

The quiet that followed was deeper than before. Not the absence of noise– but the presence of held breath.

She stood and walked over to the vent, crouching down. Her tail flicked behind her once.

She didn’t touch the grate. Didn’t peer through it.

But she could smell it now. Faint, but there. A scent that didn’t belong to her. Dust and fur and adrenaline. Not animal. Not machine.

Halfkind.

And small. Very small.

She smiled. Not in mockery. In curiosity.

“You’re not staff. You’re not a test. You’re hiding...”

Still no sound. Whoever it was, they were holding their breath.

Vesper straightened up and walked away from the vent without another word. She didn’t need to rush this. If someone was in the walls with her, she’d know soon enough. And when she did, she’d be ready.

~

Morning came the same way it always did.

Soft light bloomed from the artificial window in Vesper’s room at 7:00 AM sharp, shifting through shades of peach and amber to mimic sunrise. A gentle chime reminded her to check in. She rolled over, reached for her wristband, and pressed the flat sensor.

Acknowledged. Good morning, Vesper, the calm voice in her room’s AI system replied.

She didn’t answer. It didn’t require her to.

Her tail flicked once under the blanket, her ears twitching at the faint rustle of delivery carts in the hallway outside. Breakfast would arrive in fifteen minutes; Venison- served rare, and hard-boiled quail eggs. Black coffee, probably. She’d eat it. She’d do her stretches. She’d read for an hour. And then she’d start.

Today wasn’t about routine.

Today, she was hunting.

Not violently. Not aggressively. But purposefully.

Something had invaded her territory. Not maliciously, it seems– but it had crossed a line. It had stolen a spoon. It had been creeping through her vents like a ghost. It thought it could go unseen.

It was wrong.

She dressed quickly– tight leggings, soft tank top– and began inspecting the apartment.

Not just looking.

Tracking.

She moved slowly through the space, sniffing the air. Scent faded fast, but she had an internal map of her surroundings that most people didn’t. And something had changed. The far corner of the bookshelf had dust marks that weren’t right. A thin drag line along the shelf edge. Maybe from something pulling itself across. Tiny claw marks on the back of the side table, too small for any staffer or known halfkind.

Vesper crouched, traced one with a fingertip, then smiled.

Small. Barefoot. Deliberate.

And then, she caught a thread of scent– faint, mousey, but not quite animal. Soft fur. Clean. Female, maybe? Adrenaline-sweat. Not fear, not entirely– more like tension. Survival mode.

She was dealing with someone smart.

Good.

After breakfast, Vesper began laying out small offerings.

Not traps. Just… questions.

On the bookshelf, where the scuff marks were clearest, she placed a folded tissue. Not crumpled, not torn– just folded. Delicate. Clean.

In front of the vent near her bed, she laid a single sugar cube. No wrapper. No note. Just exposed and easy to take.

By the far corner under the sink, she placed the spoon from yesterday’s set. Not the missing one. Just a replacement. And beside it, a piece of string tied in a loop.

She knew enough about small mammals to guess the appeal of string. It wasn’t bait. It was an invitation.

Then she played the waiting game.

She didn't watch- didn't hover.

She spent the day as usual: running laps in the courtyard, stretching her limbs in sunlight, reading on the couch, attending her vitals check.

But she left her ears on all night.

At 11:17 PM, while lying in bed and pretending to sleep, she heard the softest shuffle from behind the bookshelf. Then the quietest sound- the sound of tissue being dragged along wood.

She didn't move. Not even a breath. Just listened.

At 1:04 AM, she heard the sugar cube being tapped. Then silence. No bite. No crumble. Just touch.

At 2:32 AM, a new sound. A sharp inhale– tiny, like someone startled themselves.

A whisper followed. Too quiet to make out. But definitely a voice.

Vesper grinned against her pillow.

~

Maisy didn’t remember arriving.

She remembered waking up– cold, on a steel tabletop with a too-bright light glaring down at her and the low hum of machines she couldn’t see. She remembered the sting of a needle in her leg. She remembered white walls and white gloves and white noise.

She remembered running.

She’d clawed her way out through the side vent of the observation room, squeezing through gaps meant for wires and airflow, cutting her palms on sharp screws and drywall edges. She didn’t stop until she was too tired to crawl, huddled in the dark hollow behind an air intake grate, shivering and sick with adrenaline.

That was three days ago.

She hadn’t seen another halfkind since.

Hadn’t seen a human’s face either– not up close. Just their shadows through the wall slats, their voices muffled through thick insulation. They sounded calm. Professional. Clean.

Maisy didn’t trust it.

She survived on stolen droplets from a leaky pipe, warmth from the vents near the old wing, and crumbs she scavenged from the break room when the service drones passed through the corridors at night. Her clothes were sewn together from scraps of leather and fabric she had found over the years, her cloak a discarded microfiber cloth, her belt a twist-tie.

She knew how to survive, she'd been doing so her whole life. But she didn’t know why she’d been brought here.

It wasn’t a normal lab. It was too quiet. No restraints. No barking orders. No prodding fingers. Just… a facility, tucked away from the world.

And then, she had found her-

The cat-woman.

Maisy hadn’t seen her at first. The wing had been mostly empty when she arrived– Heaven, compared to the chaos of the lab she’d escaped. The room had been empty when she explored it, too. But it radiated more heat than the others, and Maisy found herself gravitating towards it. She used the gaps in the wall to get close to the surface: near the pipes behind the fridge, the vents behind the couch, even the seam in the back of the closet.

Then the door hissed open. And she walked in.

Tall. Graceful. Alert.

Halfkind, like Maisy. But beautiful. Strong. Built like a human but shaped by something undeniably feline– sharp eyes, shifting pupils, big ears that twitched with every sound, and a long tail that moved like it had its own brain.

Maisy had frozen in place.

She thought she would be found instantly. Eaten. Captured. Battered.

But nothing happened.

The cat-woman– Vesper, she’d heard someone call her that– never noticed her. At least not directly. Days passed. Maisy stayed hidden. Watched. Learned her rhythms. She exercised in the courtyard at the same time every day. She read constantly. She cleaned up after herself with methodical precision.

And she didn’t leave food out.

Not until yesterday; That was when everything changed.

First, it was the folded tissue on the shelf. Maisy had paused, staring at it through the slats. It wasn’t trash. It was placed. Neatly. Intentionally. A signal.

Later that night, she found the sugar cube.

It hadn’t fallen from a packet. It wasn’t near the trash. It was left, right there, next to the baseboard vent where Maisy sometimes lingered to feel the warmth of the heater.

Then came the spoon.

And that’s when she started to panic.

She knows.

Maisy crouched behind the vent, breath shallow. Her hands were shaking.

It wasn’t just that Vesper had noticed her. It was that she was watching her. Testing her.

That meant she could smell her. Hear her. Maybe even sense her when she moved.

Maisy had worked hard to be invisible. She rationed her food, kept her scent minimal, only moved at night. But it hadn’t been enough.

She knew she should run. Get deeper into the duct system. Find a way out, perhaps.

But…

She glanced at the sugar cube again, still untouched.

It was the first real food she’d seen in days.

Maisy crept toward it on silent feet, body low. Her heartbeat thundered in her ears. She kept one hand on the wall, the other ready to bolt. She got close. Reached out. Tapped it with one claw.

Hard. Solid. Unpoisoned, as far as she could tell.

She pressed her ear to the floor.

No breathing. No footsteps. No drones.

She broke off a corner– barely a crumb– and darted back into the wall with it clutched in both hands.

It was so sweet it made her eyes water.

She ate it slowly, curled in a cloth pouch she used as a bed, knees pulled to her chest, cloak wrapped tight. She hadn’t had sugar in months. Maybe longer.

Her stomach ached after, but she didn’t care.

Vesper was dangerous- that much was obvious. But she hadn’t called the staff. Hadn’t tried to force her out. Hadn’t blocked the vents or set any traps.

She was leaving gifts.

Maisy didn’t know what that meant yet. But she was starting to hope it meant something.

She spent the next night thinking about the sugar cube.

Not just the sweetness of it– but the precision. The control. The intention behind it.

But she hadn't left anything to eat other than the sugar cube. Maisy was used to hunger, but this place was too clean. It was too hard to scavenge.

So on the next day, when the courtyard door hissed open and she was almost certain Vesper had vanished beyond it, Maisy made a choice.

She waited five minutes.

Watched for shadows. Listened for breathing.

Silence.

Then she moved.

Out through the baseboard vent. Across the polished floor on silent padded feet, her cloak tucked tight around her shoulders. The room loomed around her– every table leg like a tree trunk, every chair a tower. She’d never seen it in the daylight before. Never smelled it this clearly: warm fabric, faint traces of lavender, the underlying musk of halfkind fur.

Maisy darted across the floor, following the skirting along the wall. She reached the base of the bookcase and paused, heart hammering.

Above her, on the shelf, was where Vesper had left the folded tissue days ago.

A peace offering? A trap all along?

She stared up at the shelf for a long moment.

Then turned, and crept forward– out into the open, past the rug’s edge and onto bare wood.

The silence was wrong. Maisy froze.

The room felt empty… but her instincts screamed otherwise.

She turned slowly– just enough to glance upward.

And saw eyes.

High on the couch, crouched on the armrest like a statue carved from muscle and intent, Vesper watched her.

Unmoving. Poised. Eyes gleaming gold.

Maisy’s blood turned to ice.

Before she could even twitch, Vesper pounced.

Not a sound. Just a blur. A rush of air. A streak of fur and deadly grace.

Maisy screamed, turning to run– but there was nowhere to go. Her foot skid on the wood. She sprinted, cloak flaring behind her.

Too slow.

A shadow fell over her– and then pressure.

Not crushing. Not painful.

But final.

Five long fingers pressed down from above, claws extended but careful, caging her in place. She was flat on her back now, tail curled, pinned beneath the soft pad of Vesper’s palm. Her entire body fit neatly in the space between the cat-woman’s fingers.

She was trapped.

Vesper didn’t speak.

She just looked down at her, head tilted, ears alert, mouth curled into a slow, satisfied smile.

Like she’d won a game.

Maisy trembled beneath her hand, breathing fast, frozen in place. One claw brushed her side– not cutting, just tracing.

A shiver rolled through her.

Then, at last, Vesper said, voice low and almost amused.

“Gotcha.”

She was trembling under Vesper’s hand.

Not just shaking– vibrating. Her breath came in quick, short gasps. Every part of her tiny frame was coiled with panic. Her limbs, so slight and human-like, scrabbled uselessly against the polished floor beneath her. Her tail whipped side to side like a live wire.

Vesper didn’t press harder. Just kept her hand there, claws out, curved around the girl like the bars of a living cage.

Up close, the little halfkind wasn’t quite what she’d expected.

She wasn’t just mouse. She was girl. Maybe eighteen? Nineteen? Her proportions were strikingly human– more so than Vesper’s own, really. But her fingers were short and padded, feet shaped for climbing, nose just a touch rounded, whiskers so fine they were barely visible in the light. Her hair was wild and blonde, sticking out in tufts like she’d been electrocuted in her sleep. She wore scraps, visibly stitched together– clothes she had made herself?

“What are you doing here?” Vesper said, low, smooth. She was curious. Intrigued.

The girl flinched at the sound of her voice.

“Please– please don’t hurt me,” she squeaked. Her voice was higher than expected, but not childish. “I– I didn’t mean to steal, I just– I was hungry, and it was warm here, and I thought you were gone, I swear–!”

Her words tumbled out in a breathless spiral. Vesper raised an eyebrow.

“Quiet,” she said.

The girl went still.

Vesper slowly lifted her hand.

For a moment, the girl hesitated– about to bolt– but Vesper was faster. She slipped two fingers behind the small halfkind’s back, scooped her up gently, and lifted her off the floor.

The girl screamed. Kicked. Her limbs flailed, tail whipping against Vesper’s knuckles. But it was like trying to punch a cloud.

Vesper sat back on her heels, unfurling her hand slowly. She opened her palm flat.

The mouse girl now sat squarely in the center of it, knees tucked to her chest, arms wrapped around them. A shaking bundle of fluff and fight.

“Stop panicking,” Vesper said, her voice calm, almost clinical. “If I wanted to hurt you, I would’ve done it already.”

The girl stared up at her, eyes wide.

Vesper studied her. The proportions of her body. The shape of her ears. Her fingers. Her scent.

She wasn’t wild. Not feral. Not bred in a tank. She was born this way. 

But the staff hadn't told her about anyone new arriving in the wing.

“Where did you come from?” Vesper asked softly.

The girl blinked fast. Her voice cracked when she answered. “I– I don’t know exactly. I just woke up here. In some lab room. It was white and cold and– I ran. Through the vents. I didn’t even know where I was going, just away.”

Vesper tilted her head. “You escaped?”

“I don’t think I was supposed to be awake yet,” she said, her voice gaining a little steadiness. “They were still moving equipment. I was in some kind of stasis. I broke out when I heard voices. I thought they were going to dissect me.”

Vesper exhaled through her nose. Not a laugh. Not quite sympathy either. “You survived in the walls this whole time?”

The girl nodded.

“It’s how I’ve always lived- I took crumbs. Dripped water from pipes. I– I found your room. It was warm. Quiet. So I hid here...”

She looked down at Vesper’s palm beneath her. “I never meant to get caught.”

“You’re lucky you got caught by me,” Vesper said.

That made the girl freeze again.

Vesper shifted slightly, raising her hand to eye level, letting her eyes drink in every inch of the little mouse in her grasp. She'd never seen a halfkind so small before.

She was beautiful in a strange way– vulnerable, yes, but alive. Alert. Clever. Not some lab-grown mistake. Not a pet. A person.

A survivor.

“And your name?” Vesper asked.

The girl hesitated. Her voice was quieter now, small but not timid.

“…Maisy.”

Vesper’s tail flicked once behind her. She leaned in slightly, letting her eyes narrow.

“Well, Maisy. You’ve been living in my walls. Eating my food. Sneaking through my vents–”

Maisy swallowed hard, hugging her knees tighter to her chest. “I–I didn’t mean any harm, I swear–”

“I didn’t say I was angry,” Vesper interrupted.

Maisy blinked. Looked up.

“...You’re not?”

Vesper’s lips curved into something sly. Curious. Dangerous, but not cruel.

“No,” she said. “But I am interested.”

Maisy didn’t relax. But she didn’t squirm anymore either.

Vesper looked down at her, at how small she had become. 

Not physically– just… folded in on herself. Her padded fingers clutched around her arms like a railing. Her back hunched. Her tail wrapped tightly around her bare feet.

She wasn’t trembling anymore, but her muscles were taut, like she was expecting pain. Or a cage. Or the end of this strange, terrifying grace period.

Vesper exhaled slowly through her nose. Her ears twitched.

And then her eyes softened. Not completely, but enough.

She’d seen that look before. Not on Maisy– On herself.

Vesper stood up, carefully. Carried Maisy over to the couch and sat down, curling her legs beneath her. She rested her hand palm-up on her knee, keeping Maisy at a comfortable height.

No sudden movements. No more looming. The game was over.

“Sorry I scared you,” Vesper said. And she meant it.

Maisy, still shaken, blinked at her, caught off guard by the words.

Vesper’s tail flicked once, but lazily.

“I used to shake like that too,” she said. “When I first got here.”

Maisy looked up at her. She looked at Vesper's muscles- at her visible scars that spanned her body. “Really?”

Vesper nodded, eyes unfocused, memory surfacing like a bruise through skin.

“I was seventeen. They brought me in during the night, after a street raid. Sedated. Covered in dirt. I woke up on a padded table with four doctors standing around me like I was a glass specimen.”

She paused, voice low.

“I clawed one of them.”

Maisy’s mouth parted slightly.

“Did they punish you for it?”

“No,” Vesper said, almost surprised. “They… sedated me again. And then the next time, they asked. They told me what they were doing. They let me choose.”

Maisy tilted her head. “Let you choose what?”

Vesper looked at her.

“Redemption. I got to choose whether I wanted to live here and try to better myself, or get sent to a detainment centre for ferals.”

Maisy frowned. “Live here? As in– forever?”

Vesper shook her head. “No. Not in most cases, at least.”

She stretched her arm out a little, letting Maisy have more space in her palm if she wanted it. “They call it a sanctuary. A haven for halfkinds who can’t live safely in the outside world. Somewhere to be studied, cared for, protected. A recovery program. And yeah, it’s not a lie. Not exactly.”

Maisy’s voice turned wary. “But it’s not freedom, is it.”

“No,” Vesper said. “It’s… permission. With structure. Boundaries. Soft walls, not iron ones. Don't think of it as a prison, think of it as a… a fresh start.”

She looked down at her again, gaze gentler now.

“You weren’t supposed to wake up alone. Someone should’ve been there to explain all this. You were supposed to have a choice, Maisy.”

Maisy’s throat bobbed as she swallowed. Her voice was hoarse.

“So what happens now?”

Vesper studied her for a moment. Her claws fully retracted. Her fingers curled slightly around Maisy– not to trap, just to shield her from falling through the open air.

“You have three options,” she said softly. “One: I turn you in. Let the staff know you’re here. They’ll take you in, give you your own space, figure out what you are, what you need.”

Maisy shrank slightly.

“Two,” Vesper continued, “you stay in the walls. Keep hiding. Maybe they find you. Maybe you rot in the vents. Maybe you get sick. Or hungry. Or worse.”

Maisy’s eyes flicked down to her knees.

“And three…” Vesper said, slower now, “you stay with me. Here. Quietly. Hidden, if that’s what you want. I don’t report you. I don’t tell them. But you follow my rules. You don’t steal. You don’t run. You talk to me.”

Maisy looked up sharply.

“You’d do that?”

Vesper shrugged slightly, the motion fluid. “It’s not like I’ve got roommates.”

Silence stretched between them.

Finally, Maisy whispered, “Why would you help me?”

Vesper’s eyes met hers. She sighed. There was something so undoing in her tiny, watery gaze.

“Because I know what it’s like to wake up afraid, alone, and cornered.”

She looked away then, toward the window where simulated late afternoon light spilled across the rug.

“…And maybe I just don’t want to be alone in this place anymore.”

Maisy sat quiet in her palm for a long time.

Then, slowly, she unfolded her legs.

And nodded.

“Okay,” she said, barely above a breath. “Deal.”

Vesper's ears twitched slightly– not from surprise, but something closer to... relief.

There was silence for a beat. Then, she asked: "You said you were hungry?"

Maisy looked away for a second, as if hesitant to admit it again. But she nodded.

Vesper stood, gently placing Maisy down onto the couch. "Okay. Stay low."

She walked over to the small black panel on her wall– her daily request console. One custom food order per day, per subject. Standard facility policy. Nothing fancy, but enough to keep everyone in compliance and to maintain enrichment quotas.

She keyed in the request: Snack Unit – High Protein – Class E

A soft tone confirmed the order, and two minutes later the slot on the wall hissed open, and a small metal tray slid out from the intake shelf.

Inside was a sealed pouch with dried meat crisps, and a small cup of thick bone broth, still warm. Vesper carried it back across the room.

"Clear," she called to Maisy, who reappeared from behind a lounging pillow.

Vesper knelt on the ground and peeled the seal off the pouch. She handed Maisy the lid of the bone broth cup like it was a bowl. "It's not fancy, but it's food."

Maisy didn't hesitate. She reached into the bag and grabbed a piece of jerky with both hands, pulling it apart with effort. She sat on the edge of Vesper's couch, chewing eagerly, already halfway through her piece before she remembered to say:

"Thank you."

Vesper gave a small grunt. You're welcome.

By the time the food was gone, Maisy was visibly fighting to stay upright. Her exhaustion and full stomach dulled her senses. Her small frame leaned slightly sideways. Her ears twitched less. Her shoulders had drooped.

Vesper noticed.

"Come on," She said, "Let's get you settled."