Frostbites /// Douma X F!Reader (18+)

frostbites /// Douma x f!Reader (18+)

Summary: [Mermaid AU] An ecologist studying a deserted island stumbles across a creature straight out of a fairytale…or a nightmare.

✧ open season thirsts but this one turned into a full fic so fuck my life [7–8/?] ✧

Request 1: Ooh can you write yandere mermaid AU’s?

Request 2: Oh my gosh. Okay, this is so exciting. Since I realized you write for Demon Slayer I've been itching for the opportunity to see anything from you about Doma. He's just. So awful and terrible. I'm trash, I love him. He's an actual monster with a saccharine smile. I'd love to see ANYTHING from you about him. Headcanons. A scenario of him with a demon slayer, or a demon, or just some pathetic human. Even just your thoughts on him would be a blessing, your choice. I’d just love to hear anything you have to say about him. Your writing is so beautifully unsettling, (your Oikawa piece Fanatic. That left me thinking about him for weeks.) So anything about Doma would be fantastic. But no pressure, if Doma isn't your cup of tea please don't force yourself. Honestly I'm just excited to see what you write from any of your requests. Thank you for being so lovely!

A/N: Combined these requests bc I feel like Douma was honestly perfect for this, and I’ve been holding off writing him until he gets animated but who knows how long that’ll take. Thank you so much, btw—I’m also Douma trash and I’ll absolutely be writing more for him in the future!

Is this yandere? It’s more like an origin story of Douma going yandere for cute ecology RA!reader. I haven’t written a scene like this in ages and it was really fun! I know I’m cursing myself by saying this, but maybe one day I’ll write more in this AU…no promises though ♡

Tags/warnings: yandere, mermaid AU but more on the spooky side (shoutout to @yandere-daydreams, the og yan mermaid fucker & a huge inspiration—thanks!!), fear, action, blood kink (?), mild violence, horror/beauty paradigm, size difference, animalistic, HEAVY predator/prey dynamic, one-sided sexual implications (reader is oblivious), ‘it’/‘the creature’ , hand kink, OSHA violations, there are many benefits to being a marine biologist, unfinished business…

You’ve never slept well in the cold.

Maybe you should’ve kept that in mind when you applied for a research assistant position on a tiny, uninhabited island off the Russian coast, but you thought you’d get used to it. You were sure—you were so sure, cocky little past-you—that you’d adapt to the below-freezing temperatures, that the worst part about the 2-month long field study would be the boredom of spending your days taking water samples and tagging birds with no cell service. But it’s not. The worst part is the cold.

So technically, one could argue that there’s a decent reason for you to be out of your bed tonight, yes? You couldn’t sleep from the stiff pain lancing through your sore muscles and the cold, so you made the (undeniably stupid, you’re now realizing) decision to leave camp and wander through the forest looking for…something. But by now you’re starting to regret it. You don’t think you’re far from camp, but everything feels sharper and stranger when you’re alone like this—the collar of your heavy jacket chafing against your throat, the crunch of hoarfrost under your boots, the thin beam of your flashlight catching the steam of your breath here and there before glancing over the surface of the water. God, you should have stayed in bed.

Even so many hours past sunset, the river that cuts through the center of the island is darker than the night and twice as cold. You haven’t forgotten the cautionary words the team leader imparted on your group before you came to the island: how easy it would be to get caught under the current, how quickly the icy water would seep into your limbs and your blood and your heart. You’ve been following the river because there are no paths and no markers, but you keep a safe distance—that is, until you see it.

A flash of light reflecting back from something under the surface. A rippling tongue of silver cutting through the black water. You start, shiver. You look again for the fish (how could it be a fish, though? nothing that big lives in the water here) but the churning waters are dark again. Just to prove to yourself that you’re being silly, you take a few slow steps closer to the bank—crouching low to keep your balance, shining your flashlight into the river, straining your vision to stare into the depths.

And someone—something—looks back.

You know about the fight or flight instinct, how the nervous system kicks into gear with the right stimulus; that reminder that humans are prey animals too. But you don’t run, and you don’t fight. Every muscle in your body stills, locks into place. You freeze. The thing in the river places its hands on the bank to rise half out of the water and tilts its head to the side; stares into your face. And you stare back at it. Behind it, in the river, you see hints of what caught your eye earlier: a silvery tail, like a fishtail but impossibly long, winding effortlessly through the water and keeping the creature’s torso afloat.

Your knees and the heels of your palms press into the ground. The ice underneath stings through each layer of clothing that was supposed to protect you from the elements, biting a little deeper with every second you spend sitting rigid and looking at the creature in front of you. Run. Run. Run, you think.

It blinks slowly, pale lashes shuttering down over kaleidoscopic eyes that your mind can’t seem to categorize into human or inhuman. You’re so focused on its face that you don’t see its hand move, don’t even know it’s reaching for you until you feel the icy weight of it against your cheek. Its lips part—those teeth, oh god, oh god—and it speaks something in a low, eerie voice that you know by instinct wasn’t built for human language.

(You don’t understand then—the version of Japanese he learned so many decades ago was too archaic and too heavily inflected by his unnatural manner of speaking for you to comprehend. Later, when you’re able to understand him, he’ll repeat what he said that first time he saw you kneel down by the edge of the water like a frightened doe: he’ll tell you he laid his hand on your bare skin and felt the beat of your heart and did his best to remember the human word for warm.)

But you hear different.

You hear the whispered, slithering curse of a monster from a nightmare—a beautiful one, but still. Your prey instinct thrills into pure terror, and finally a thought rips its way to the surface. You know—your brain knows, the logical part of you that you’re supposed to rely on—you know what you need to do. You have to get away. Heave your shivering body off of the muddy snow and force it into motion. You know this, you should know this, and yet the fear radiating through your body is concentrated not on your legs, but on the point where the—

—the what? the mermaid? the monster?—

—this thing is touching you, its fingertips resting delicately on your cheek. The body below the human torso resembles something between a shining fish and an eel, but the skin touching yours would almost feel human if it weren’t so cold. (Like a dead man. Like a dead thing, your mind tells you, and if every hair on your body wasn’t already pricked up in goosebumps, it would be now.)

The nails, too—not like a person’s nails you’ve ever seen—thick and long, tapering into points that could tear your flesh open like paper if the thing in the water decides to move them just a fraction of an inch down into the delicate tissue of your cheek—and because you can’t stop yourself, you don’t do the sensible thing. You don’t run. You release something that sounds like a choked scream (you can see the steam of it staining the frigid air white more than you actually hear it) and you force your stiff muscles to take hold of the creature’s wrist and try to drag his hand somewhere, anywhere it isn’t touching your face.

Stupid. Stupid. Stupid. You’re going to die here, aren’t you?

The terrible, beautiful form before you flexes, rippling like a current’s passing down from where your covered fingers are feebly trying to pull at the cold, thick mass of its arm; in an instant, it’s lifting itself out of the black water to tower over you, and it—

Not it. Him.

The thing, the monster in front of you isn’t human, but from the waist up you can’t help categorizing it—him—as male in your head. Even without considering the dozen feet of his tail, it’s a body with power threaded into every centimeter of flesh: muscular, serpentine almost, and larger than a human man’s but unmistakably male, even if the slick contours of his abdomen, his pectorals, the V-shaped muscles framing his hips and disappearing into scales below would be better suited to a stone carving of a pagan god than any man you’ve ever seen in real life.

The wrist you naively thought you could move is so large that despite the added bulk of the mitten you’re wearing, your fingers aren’t even close to meeting around it; when he bows his head toward yours, forcing you to arch your own neck back to avoid another unwelcome touch, the pristine architecture of his face fills your field of vision. In the periphery, you see a few wet strands of silver-gold hair slip over his shoulder and onto the surface of your puffer jacket, dripping frigid river water into the nylon and the fill until it soaks through to your collarbone.

More important than that, though, is the way he’s looking at you. He’s surprised, or you’d think so if this were a human and you could trust your interpretation of his wide eyes and his head cocked to the side, the slight part of his mouth and the way it curls up at the corners—some mixture of shock and delight, like a child who’s managed to catch a bird in his hands and can’t really believe his good luck.

You feel the muscles in his arm contract and then the grip you had on him is inverted—it’s him squeezing long, agile fingers around your wrist, easily spanning the width of it even over the thick sleeve of your jacket, nails stroking over the fabric like he’s deciding whether or not to shred it to get at your skin.

After a moment of deliberation, where you scrunch your eyes closed and grimace away from the cold seeping off him in waves, you feel the synthetic texture of your insulated mitt slipping over your hand—he’s taking your mitten off? You chance a quick look over, and he’s already tearing through the thick wrist strap with a single swipe of his claw to pull the mitt over your hand and drop it limply to your side. It’s too cold here for bare hands—you instinctively try to draw your hand back, curl your fingers into a fist, but the creature doesn’t let you—a short hiss escapes his mouth, and then his own hand is flattening against yours, forcing your fingers straight so he can—

—it’s strange. Almost like he’s comparing the size of his hand to yours. But that wouldn’t make sense, would it?

With the damp cold of his palm aligned against the warm softness of yours, you can tell that his hand is enormous—each fingertip outstretches easily five, six centimeters past yours, even without the added length of his sharpened nails. The stillness, the strangeness of the comparison quiets the part of your mind that’s curled in on itself with sheer terror enough that the researcher in you can start making notes—skin resembles human’s but slightly…smoother? glossier? could be something covering the surface along with water—abnormally large hands but seem to correspond with body size—small amount of transparent webbing between the fingers…

The massive hand pressed into yours shifts by a few degrees, fingers finding the gaps between yours, lacing your hands together and applying pressure until, until—

You flinch, trying without success to yank your hand away from the source of the pain and you speak without thinking. “—stop—stop, that hurts!”

He stops, easing the pressure on your delicate hand, but only by a little. Curious eyes move back to you, lingering over the movement of your mouth when you speak. His own mouth opens, and you force your gaze back up to his multicolored eyes so you don’t have to look at his teeth.

“h—ur—hur—ts?”

You frown through the persistent ache in your wrist—did he just—? Is he trying to imitate you?

“hur—ts?” the creature says again in that low, slithering voice that still feels wrong somehow. “it—hurts?”

“Can you understand me?” you gasp, the words leaving your mouth so quickly that your breath in the cold air clouds his beautiful face for a moment.

His head dips into a fluid nod. “—can— un—under—stand.”

You’re marveling at the discovery—not only can this creature sort of…mimic human speech, it seems like there’s a chance he actually understands what you’re saying. Does that mean he’s met humans before? Is he part human—some kind of human hybrid, a species never before believed possible until you stumbled across it on a completely unrelated research project? What does this mean—for your team, for your career, for the world? Never mind that he’s still gripping your hand so hard that the bones are starting to throb with pain—for the first time since you spotted his tail moving through the water, your fear moves to the back burner. Instead, your mind is humming with the possibilities of this finding.

Which is why you don’t notice him leaning in closer until it’s too late.

“sm—ell— g—ood. smells—good,” he repeats breathily, the air exhaled from those unearthly lungs washing like a cold rain over the side of your cheek. His face—so much larger than yours—is nudging up against the place where your jaw meets your throat, breathing in your scent. You can feel the brush of his pale eyelashes against your sensitive skin.

“want to— t—taste—want to—eat—”

You’re so numb from the cold that you barely feel the razor-like edge of his claw slice through your bared skin, drawing a shallow cut from your thumb down the back of your hand to the bulge of the carpal bones in your wrist. It’s not deep—the pain isn’t even as noticeable as the strangeness of the heat you feel seeping from the injury a second later—which you realize, as the creature pulls back just enough to lick over it—is blood.

Your blood.

He’s lapping at your blood.

You try to scramble to your feet, boots scraping haphazardly against the slippery coating of snow on the ground only to pull him closer by his grip on your hand when you stumble back almost flat to the earth. You prop yourself up on your elbows and then he’s looming over you, nose almost touching yours, the bulk of his broad chest gleaming white like the snow underneath you.

He’s smiling—beaming down at you, eyes wide with joy, such an angelic kind of beauty that for a second, despite everything, your heart seizes up with longing—ribbons of metallic hair curl around his face as they dry or drip down over his chiseled shoulders like rivers of gold—his eyes shimmer in a million colors you couldn’t put names to, almost luminescent even in the scattered halo from the flashlight you discarded a few feet away without thinking—this monster, your angel of death staring you in the face, so beautiful it hurts to look at him—

Stop freezing. You have to run. You have to do something. Your adrenaline isn’t working right, it’s pinning you into the frozen earth just as surely as the creature on top of you. The weight of his body—the juncture between his human abdomen and the tail—settles between your knees, forcing your legs wider to accommodate the mass between them. His mouth moves and again you’re transfixed piecing together his fractured speech.

“you—taste good—soft— sw—sweet. want to—touch—feel. inside.” His low, raspy voice is laced with something besides pleasure—hunger? you can’t tell, you’re not sure, but it has to be—and his eyes drift closed happily as he speaks, one thick arm curling underneath your rigid body to draw it up against his. “let me—inside—? let me feel inside—”

“Get off me!” Do something. Now. You don’t know what he’s talking about (‘feel inside’? what the fuck?), but considering common sense is telling you that there’s a decent chance you’re about to be wolfed down like Christmas dinner, it can’t be anything good.

You struggle awkwardly against the pressure of his arm, but you’re nowhere near worming your way away from him when your bare hand scrapes roughly into the dirt near your leg searching out the pocketknife you keep zipped into one of your chest pockets. Somehow you have a hard time believing the 6cm blade you use to clean under your fingernails is going to do a whole lot of good against the literal monster that’s wrestling you into the snow at the moment, but maybe a decent slash over the face could distract him enough for you to get away?

It doesn’t matter, though—as soon as the back of your thumb makes contact with the rough fragments of ice littering the ground, your escape attempt is thrust to the side in deference to the line of fire screaming out from the cut on your hand. A mixture of clean and dried blood smears out over the dirty snow and you have to bite your tongue to stop yourself from whimpering like an animal.

The pressure against your chest lets up as the monster…sits up, or whatever the anatomically-correct equivalent position is, staring down at you with patronizing concern over his face. “it hurts?” he asks slowly, almost mockingly, but your eyes are fixed on the newly-reopened injury spilling a few final drops of scarlet into the white canvas underneath. So red, like…

The flare.

The fucking flare you were given, for emergencies only.

You’re an idiot.

Before the creature can resume its attack, your abused hand shoots to the thigh pocket where the flare is resting parallel to your leg—you can barely get your cold fingers to move to the right position but you force the stiff digits to grip the zipper and yank it open, bending a few of the metal teeth in the process. He notices you moving, but just cocks his head to the side again, waiting patiently to bat aside whatever pathetic resistance attempt you’ll mount this time—and then you have it—the long rod of the flare is resting in your hand and you slide it out of the pocket to point it out to the side as far from your body as possible—

his eyes narrow a little and he makes to reach out for you again, probably wondering what you’re holding—

your team leader taught you how to use these flares on the first day of the boat trip: hold it downwind remove the cap strike the lid like a match—and in the chaos you barely remember to turn your face away and close your eyes but you do and then—

Heat explodes through the icy air as the black behind your eyelids blooms scarlet from the light of the flare. You can hear it hissing and spitting—or is that the monster?—but more importantly you can feel it, the fiery warmth roasting through the darkness at the end of your arm. You thrust the flare upward blindly (careful not to let it anywhere near you but so desperate at this point that you’d take a nasty burn over being eaten alive) and an instant later you feel the weight of his body lift off you. You don’t have any time to waste—it’ll only burn for a minute, and with the frost still biting through your lungs you’re not going to be running as fast as you’d like—but hey, he’s part fish, right? So all you have to do is get away from the water. At least…you hope.

56 seconds left. You toss the still-burning flare to the side and roll in the other direction, squinting through the all-encompassing red glow to make out the plastic glint of your flashlight. You spot it, dive for it, and wrap your undamaged hand around the familiar grip, tucking the other into the pocket of your jacket for warmth. 49 seconds left. You can hear him behind you—growling or something in that creeping voice—but you can’t look back. Can’t look into those eyes, or you’ll be trapped again, pinned and licked and taken. You haul yourself to your feet and pick a direction—doesn’t matter where, as long as it’s away from the scarlet fire of the flare and the river and him. 43 seconds left.

Behind you, the growling has started to sound like laughter.

Run. Run. Run.

///

In the morning, you wake up cold.

You’re nested in your bedroll, but icy sweat is soaking through the fleece lining of your undershirt and your whole body is shaking trying to get you warm again. What a horrible dream, you tell yourself. Just a bad dream. You’re still wearing your outdoor jacket but that must be because you were so tired after the job you were assigned yesterday that you forgot to change into your nightclothes, so silly. One of your hands feels prickly and achy and it stings but that must be because you scraped it on something while taking samples. So careless of you. What a horrible dream, you tell yourself.

The morning light filtering through the tent is silver-grey, almost gold at some angles. You stare into the perfectly normal light, straight up into the place where the sun should be behind the fabric. There’s condensation collecting on the ceiling of the tent; when it drips down onto your bare face, you have this strange idea—that the sudden shock of cold water spilling down your cheek feels almost like…

…almost like the echo of a touch.