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Living in the walls of a monsters home

Summary:

My Name’s Casey, I am 16. and...
I'm a Borrower… which means I’m only about 2 inches tall.
This makes life... Difficult to say the least.
I've been living in the Dreemurr’s house ever since I can remember…

AKA a Deltarune Borrower au with some oc's...
or a self-indulgent fic that I never planned on posting...
till now.

Chapter 1: living in your walls

Notes:

(See the end of the chapter for notes.)

Chapter Text

My Name’s Casey, I am 16. and...
I'm a Borrower… which means I’m only about 2 inches tall. This makes life... Difficult to say the least. I've been living in the Dreemurr’s house ever since I can remember…My mom (Ruth) and dad (Lev) have been teaching me how to borrow Ruth, letting me go on trips with Lev. It was scary at first, the difference in scale, but I got more accustomed to it, that was until. Mom and dad disappeared one day… not returning home…

I was terrified, not knowing what happened to them. the worst was all I could imagine… abandonment, killed, eaten… It made my skin crawl…

That was four years ago now…

I had gotten better at borrowing using my parents left over supplies to scrape by. It was hard but it was just life.

The Dreemurr’s were a particularly interesting family mainly because they housed the only human in town. Kris. The mother (Toriel), father (Asgore) and son (Asriel) all being goat monsters… they often had another family over the Holidays made up of four reindeer monsters. mother (Carol), father (Rudy) and their two daughters (Noelle and Dess). It was weird watching the two families change over time… living in the walls by the staircase means it’s kinda unavoidable to not hear everything.

I had basically grown up with Kris… it was strange seeing another kid my age but being unable to interact with them. I watched them grow and change along with me… My parents went missing around the same time as Dess did. That’s when I watched things fall apart…

Toriel and Asgore got divorced taking a massive toll on Kris and Asriel… the Holidays stopped visiting… I heard about Rudy getting sick… Kris started to further isolate themself not talking to anyone… and next fall Asriel leaves for college. I could tell it was weighing heavily on Kris…

Kris had stopped wearing their red horned headband... It was strange seeing all this happen… I wanted so badly to comfort Kris… but it was against the rules… Borrower code forbids me from being spotted if I am, I’d have to leave… but I had nowhere to go… One late night in May after the house was asleep… I headed up to Kris and Asriel's room… using one of the makeshift elevators to the second floor, then following the tunnels under the floor to the opposite side of the room by Kris’ bed.

I walked up to the shortcut in the wall. setting my borrowing bag down just within the wall. I was starting to have second thoughts, but I continue anyway. I walk out being in between Kris’ bed and the wall… I pull out my makeshift grappling hook, made from twine and an old fishhook.

I swing it and latch it to the edge of the bedframe. Tugging a few times to keep it secure, before hoisting myself up climbing the rope to the bed’s edge. I untie the twine from my waist. Leaving the hook in case I need to run. I climb up the rest of the way using the bed sheets. soon pulling myself up onto the bed. Seeing Kris, sleeping soundly. They were laying on their stomach; their head turned toward the wall… toward me.

I took slow shaky steps toward them. Seeing their hand lying flat next to their face, arm limp at their side disappearing under the blanket. I was soon standing right in front of their face; their bangs covering their right eye. Left eye closed, slow steady breaths coming from their slightly agape mouth. My heart was pounding seeing their towering form in front of me. It made my heart feel strange... my tail curled close to me. I should just leave…

But I stood there for a while debating with myself on whether I should leave or not. I then hesitantly placed a hand on Kris’ cheekbone right below their uncovered eye. Their skin was warm… it was odd being this close to the bean… this close to someone… it had been a long time…

Maybe all the warnings and assumptions I heard about humans and monsters were wrong…

Just as the thought enters my head my heart skips a beat as I watch as Kris’ eyes scrunch up…

Their mouth closes forming into a frown. A rumbling hum coming from their chest… I shiver, pulling my hand away and backing up as their eye blinks open, squinting in the dark… their one uncovered eye looks around for a moment then locks onto me… my fur stands on end, as their eye widens. I need to run… their visible hand starts to move. I scramble to sprint around it heading for the edge of the mattress. I hear them push themself up behind me… making the mattress wobble. almost falling; I don’t look back.

I drop down the edge clawing my way down the sheets to the bed frame. I hear them groan above me. I climb down to the makeshift grappling hook still attached to the frame and make my way down to the floor. Retrieving the hook by snapping the twine like a whip getting it to release and fall to me. I don’t bother tying the twine to my waist, no time. I rush back to the crack in the wall. Heart pounding in my ears, I look up seeing Kris staring down at space between their bed and the wall… at me. I freeze up, for a moment as they stare… brown eyes dilated from the darkness it’s hypnotizing… I shake my head, snapping out of it, slipping back into the wall.

This was a mistake…

Now they know. I grabbed my Bag and made the long journey back down to my home in the walls. I take a breath trying to keep my heart from exploding. Kris saw me…

They saw me…

They didn’t hurt me they just, stared…

I knew it could end badly whether I leave or not… but for the time being it was better and safer to just stay.

-

I was woken up that morning to the familiar sound of thunderous footsteps coming downstairs… and Kris… talking with Asriel… they were in the dining room. I uncurl my tail and body sitting up. starching my arms trying to stifle a yawn. My ears perk up trying to make out the words…

“I’m not lying! I saw a tiny person!” the voices slightly muffled by the walls around me.

“You sure it wasn’t a mouse?”

“I’m sure! It looked human! kind of…” Kris seems more unsure.

“Heh, what do you mean kind of?” Asriel questions.

“I don’t know, it had a tail… and fur…” I slip out of bed, my nervousness sky rocketing, as I hear Asriel hold back laughter…

“I’m not Joking Azzy! I saw it!” the sound of footsteps walking past my home entering the room, Toriel…

“Hey mom,” Kris and Asriel say in unison.

“Morning, are you too ready for breakfast?”

“yeah” They both say I hear them move to the table.

“Kris thinks they saw a tiny person last night,” Asriel bluntly says… I can practically feel Kris’ glare at Azzy.

“Oh. Well, I’m sure it was just a mouse,” Toriel assumedly says. Kris doesn’t respond.

“Well, we should get some mouse traps then, huh.” Azzy says Kris stays quiet. my blood chills under my skin, mouse traps… that’s bad.

“Oh, that’s a thought, maybe you and Kris can get some when you head to the store later?”

“Sure, sounds good. Would that quell your nerves, Kris?”

“Yeah, I guess…” as they speak, I can tell Kris’ lying… they’re going to start using traps, huh. Never dealt with those before…

The day passes as normal… I stay in my home all day… just listening in on occasion… it was a Saturday… relatively calm. All things considered.

-

It’s been about a week since Kris saw me, the teen had become hyperfixated on catching me. setting traps around the house… it seemed more like they were trying to distract themselves from the thought of Asriel leaving… but it still scared me the way it was escalating. They first started leaving food out trying to catch me, then glue traps… when those didn’t work…

it got worse...

Another week passes when I get an idea… I leave a note next to a trap with the words “try again” Kris’ reaction was priceless; their panicked expression and excitement was worth it.

-

Two weeks passed now into June, and I’d leave more notes every time I’d discover a new trap. Using a batch of usable-to-size pencils I’d made for myself a while back. Seeing Kris get flustered about the notes was funny every time. They started leaving more traps and even making their own. Trip wires, tiny snare, and crude handmade box traps… it was fun for a while that was until. While getting ready to go on a borrowing trip one night… I had three young Borrowers appear at my doorstep…

Mae Casper, and Leslie… this was bad. Now I had something to lose…

Mae and Casper were twins, both 13… but Leslie was only 8… they had lost their parents a few months ago… where exiled from a colony and had been living outside for a while… but found my place after wandering the woods for about three weeks… they looked more like mice than I did… light orange-y fur. I helped them get settled letting them stay in the main living space… not wanting them in my parents’ old room.

They were nice but… it was hard having someone my size around again… I had gotten so used to being alone… often having to apologize to them about talking to myself out loud…

I waited a few days to tell them about the inhabitants of the house… telling them about Kris in particular, and primarily the traps… at first, they were a bit freaked out. I tried to reassure them saying they don’t have to go out and can just stay home… stay safe.

I took a while to convince Mae not to leave immediately. But she eventually agreed to stay after a few harsh conversations.

Mae was the first to offer to go with me on Borrowing trips… she felt it would be safer if we stuck together but… I refused. I couldn’t let them get killed. Not due to my negligence…

-

It was summer now… July to be exact. Asriel had already got accepted by a college out of town… he was going to start in September… Kris was clearly hiding their worry of being left alone, one day they came home with a red wagon and bird cage… it confused me, along with Asriel but Kris didn’t give an honest answer… what did they need it for?

Kris was hiding something; I wanted to know what but… I can’t just ask, and even if I did, it could end badly… for me and my three new friends.

Notes:

man, I've haven't posted to Ao3 in a long time...
I even deleted my old works.
hope anyone reading enjoys this at least a little.
I know it's very self-insert-y but that's what I like writing.
Constructive criticism or suggestions are welcome.
I do have a few more chapters planned out, unsure I'll post them tho...