Written for my girlfriend, and originally posted on AO3. The sequel will be posted later!
I can feel the groans already 'another mermaid au...?'
yes, yes it is. The twist I can offer is the fact this is an already established relationship the readers are getting a peek into, opposed to a long meet-cute narrative. Nothing against that, but I wanted to do another take on it! This time with some additional cuteness of cool aunts taking care of their nibling.
as a note, this is unbeta'd, so I'll swing back in later to edit it.
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"I can't believe you even go near that house. Its so… creepy!" Kid broke Frisk's concentration, the dark haired child glanced up from rummaging in their backpack to peek at their friend. "Seriously! No one has ever seen the owner like ever!"
Frisk shrugged back, offering Kid an easy smile in turn. Frisk closes up their backpack, giving up on finding their book to slide the bag back on. "It's not creepy at all. It's really nice actually." Frisk paused briefly before adding, "I'm pretty sure people have seen her before..."
"Cre-epy! With a capital C!" Kid repeated with a stamp of his foot nearly setting himself off balance. Years of practice kept him from falling flat on his face. It wasn't uncommon Kid fell, but he at least was learning how to avoid it. "If you're gonna go there, I'm gonna go home."
"Alright. Remember to finish your book report. Its due this week."
"Okay, okay! Good luck with creepy town!" With that Kid scampered off, the armless eleven year old was not about to linger when it came to the weird beachfront house. The estate was an relatively old one, spruced up by owners a decade ago and quickly shut in. The great wrought iron fences extended from the grassy front to the edge of the beach where it rested. Large signs declaring it was private property hung everywhere.
Frisk could guess why some people could be put off by the place. Frisk just felt nostalgic whenever they walked here. They remembered learning to swim in the waters here, sunny days spent playing piano and skipping stones with their aunts. Not the unease people felt when walking by.
Frisk watched their friend go before turning towards the front gate. With no hesitation the child punched in the pass code, stepping forward after the automated gates finished swinging open. Frisk offered the gates a friendly pat before making their way across the sandy dunes that made up the front lawn of the estate. Distantly they could hear the gate snap shut and lock behind them. Frisk offered the animals living in the yard a friendly wave or greeting as they passed. The young child only paused their journey to slide out of their sneakers and socks, balling up the socks to stuff in their shoes.
The walk was always the daunting part. Frisk had preemptively taken their shoes off for this journey, but they suspected they'd still get sand in their sneakers somehow. No matter the occasion, sand always seemed to find its way into their shoes and clothes. Toriel never seemed to mind, but the child didn't want to bother her with sand.
They hop over an old fallen log, trailing to the front steps, skipping a step and landing on the next with a satisfying thump. Frisk does it again until they reach the porch. The quiet child set their belongings aside on the porch swing, turning back to the door to ring the old dusty doorbell button.
Frisk simply rocks backwards and forwards on the balls of their feet as they wait. They can hear a piano distantly stop and shuffling before the sound of a familiar heavy gait approaches the front door. The door handle jiggles in its usual fashion (along with Frisk hearing Alphys sigh about needing to fix it) before the door opens.
Alphys blinks owlishly behind her large glasses, wild golden graying curls looking rather rumpled a she smiles down at the child. Her wild curls framed a dark complexion with light freckles and laugh lines curled around the edges of her mouth. When she smiles, Alphys reveals her uneven teeth.
"H-hey, Frisk. J-just on time! C'mon in."
She steps aside readily, letting Frisk enter. Frisk gladly steps inside, dusting their feet off on the welcome mat out of habit.
"You're such a good kid. Geeze." She laughs, reaching out to ruffle Frisk's hair. Earning a hug from the child after they hopped over the welcome mat. "Big sis s-s-sure drilled those manners in, huh?"
Frisk just snorts, pulling back to pose dramatically. More or less mimicking a pose they saw Mettaton do on TV a few days back. "I'm just naturally this great."
"O-Oh my god." She laughs loudly back, she covers her mouth to try and stifle it. Frisk just poses harder to prove their point, flexing a little as well. If they do it well enough maybe they can summon sparkles like Mettaton did on tv.
"HEY! Don't leave me out!" Comes from the next room. Undyne making herself known. "What is the kid doing?"
"Y-You don't wanna know!" Alphys gives Frisk a small smile before heading in the direction of Undyne's voice. A section of wall divides the two rooms, crossing it leads to a large pool of water with a piano settled on a pedestal in the middle of the pool. The pool takes up most of the room, what is left is a large flat screen TV on the wall and ratty water logged couch nearby covered in cushions.
A stain glass window lets the late afternoon light pour in over the room, bright colors glittering against Undyne's deep blue scales. Webbed fingers brush across the piano's keys fondly. The sight is as familiar to Frisk as their own apartment is. They swam in these pools, played piano, skinned their knee from running indoors. Nearly broken the stain glass window with Papyrus.
Undyne sits on the bench in front of the piano, irritably flicking her tail back and forth. She brightens up considerably when they two walk in. The fins on the side of her face perk up, shimmering with fresh water. Her one good golden eye snaps to Frisk. She grins, showing off rows of choppy uneven yellowed pointed teeth. One or two have lost their tops or completely fallen out to grow in anew.
"Good to see ya, punk." The mermaid pushes off of the bench, gladly splashing into the water with dramatic flair. The dark blue mermaid surfaces again at the edge of the large pool, red hair sticking to the side of her head as she grins up at Frisk. "Now, give your aunt a hug, you little nerd." She rises and Frisk has no hesitation in giving their aunt a hug. Even if she's a fish and wet. A wet fish hug is great.
"Good thing I have spare clothes for you here." Alphys muses in turn, "T-Toriel would kill me if you got sick."
"Bah. It builds character!" Undyne slams a fist against the concrete, leaving another dent along several other hand shaped dents on the edge of the pool.
"I'm not picking a fight with T-Toriel." Alphys stated back. The sixty year old woman walked over to the wall pressing a button on a console. There was only a brief pause before mechanical bridge unfolded from the piano's island to the edge of the pool.
"Ya wimp." Undyne scoffed, moving to submerge herself back in the water, swimming back to the piano island. Frisk gladly walked across the bridge, standing next to the bench. Undyne emerged from the water, throwing herself up and landing awkwardly on the bench. After some shuffling she manages to settle, turning to Frisk. "Get over here, I need my peddler!"
The afternoon goes as it always does, Frisk learns a bit more about playing the piano before Undyne's unbridled enjoyment sweeps her away to writing some kind of ballad or slamming out a song from memory. Frisk frantically tries to keep up with peddling for each song best they can. Alphys vanishes mid-way through towards the direction of the kitchen.
"I-I Hope you like sushi." Alphys announces, arriving from the next room with a tray in her hands. Frisk nods readily, already knowing it's one of the few things the two women can 'cook' without burning down the house. The eleven year old slides off the bench, moving to cross the bridge.
"Hel- heck yeah." Undyne quickly corrects herself, fins slapping against the side of her head at her mistake. Her enthusiasm kicks back in steamrolling over her gaff. "Heck yeah, sounds great, babe!" Undyne leaps off of the bench, splashing into the water dramatically before resurfacing at the edge. Her good eye glued to the tray Alphys brought out. Frisk could see her tail swishing predatorily in the water from where they were standing.
The blonde woman pulls up a few seating cushions, dropping one down for Frisk and herself. After settling down she pulls out their utensils for the meal. "H-Here." Alphys cracks apart some chopsticks, handing them over to Frisk first before doing the same for her wife. Undyne simply grins, toying with the chopsticks before slamming them forward to stab an unsuspecting roll. Bits of rice, fish and rice paper go flying in the process. Alphys doesn't seem particularly bothered when rice pelts her shirt.
"If the fish falls in there, you b-better eat it."
"Dam- darn right I will!" Undyne spares Frisk another glance sinking back into the water slightly. Alphys just eats contentedly, leaning back slightly. An easy and familiar silence settles over the three, only broken up by Undyne's occasional battle cry at a particularly boisterous sushi roll. Frisk ducks bits of rice and deflects a stray piece of fish back at their mermaid aunt. Undyne catches the stray fish in her mouth triumphantly.
"Frisk I've been meaning to tell you this." The lack of stuttering makes the eleven year old pause, glancing in the direction of Alphys. Determination written across her features. "It's something your mom and I have been t-talking about for awhile."
Frisk gives Alphys a moment to push forward with her statement, Undyne being uncharacteristically quiet in the moment. "The neighbors nearby are going to move soon, in a few months. I-I and your mom thought it would be nice if all of you could live closer." Frisk nearly drops their sushi roll at that, blinking in surprise.
"You come over so often and our place is closer to your school." Undyne adds, rolling her chopsticks across her knuckles. She shares a glance with Alphys. "So we're probably gonna chip in to buy you dorks a new house. Your mom wants to pay for it all, but hell no!" The chopstick goes flying as Undyne slams her fist against the concrete. Alphys watches as it tumbles and falls into the water. All she can do is cover her face with her hand.
"No way in hell are we letting Toriel, Sans or Pap or you toil in that shit hole of an apartment anymore! You're too good for that city crap!" She pauses. Fins slapping against her cheeks again in wordless self admonishment. "No way in heck, er. You get what I mean."
"Really?" Frisk finally finds their voice, glancing between their aunts curiously.
"Y-yeah." Alphys toys with her food nervously, "I-I mean. I-If you're okay with it. We're passing it by you since you're part of this too."
Frisk simply hugged Alphys nearly sending more food flying before scooting over to hug Undyne. "I-I'm going to take that as a yes." Alphys nervously laughed, relief clear in her voice.
Dinner ends up being more talkative than before, the three talking about moving plans amongst bites of sushi. Predictably more food goes flying during the excitement. When bedtime rolls around, Frisk stumbles towards the guest room with little complaint. They hear Undyne flip back into the water, likely swimming to her and Alphys bedroom.
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"O-Oh my god." Alphys hid her face in her hands, feeling a silent scream coming on as she went over the day's events. Undyne's touch and subsequent weight rolling onto the human distracts her from the silent scream. Undyne's loud voice equally distracts the graying human woman. "Today went great!"
"It did. I-I was worried."
"I could tell! You were sweating bullets before the kid even showed up." The very large slightly damp fish answers, settling in Alphy's lap, their water bed jiggling under them from the movement. "I told you! Frisk was so for it!"
"I-I know!" She squished further into the bed, stroking her hands across Undyne's tail for comfort. The smooth scales had become something of an anchor for Alphys to touch over the years. Some part of her is surprised there aren't grooves from her idle stroking by this point. "D-Doesn't mean I was going to feel better until I did it."
Undyne leaned forward to press a kiss on her spouses lips. Nuzzling into the human's neck happily after breaking away from the kiss. Alphys could only melt at the attention, feeling her face go hot. "Looks like we gotta heckle that Jerry guy into moving now."
"We're not throwing rotten fish in his yard."
"It's a valid strategy!" She protested, squirming off of Alphys to the edge of the bed to scrounge in the pool next to her side of their bedroom. She emerged with some sea urchins in hand. "Look, I can settle for just these. They've got a real kick." Incredibly poisonous sea urchins were rare but Undyne always had a few nearby.
"O-Oh my god, noooooo!" She swatted vaguely in Undyne's direction, not making connection in the least. "Yeesssss!" Undyne waggled the urchins in her wife's direction before dropping them back into the pool. "Or I could lurk in his water, make him think it's shark infested." She snapped her teeth threateningly, making a clawing gesture.
"If you got harpooned I'd be so mad. You nearly got hurt last time you- you lurked near someone's house." Now the swatting connected, be it very lightly.
Undyne shrugged, "You don't live as long a I do without some cool scars." She helpfully flexed back at her wife, "SEE!" As if it was the first time she had seen the variety of strange scars littering the mermaid's body. "Means you gotta live dangerously!" Which involved lurking neighbors water and occasionally frightening people who trespassed. People already assumed the beaches nearby had sharks thanks to Undyne.
Alphys found herself staring before shaking her head, "N-no way! Don't distract me with your... rugged good looks." Her voice dropped several degrees, partially whispering it. Alphys was half afraid Frisk would walk in. That and Undyne just laying on their bed shirtless was making the 60 year old incredibly sweaty.
Undyne simply flexed a little more, leaning forward. "Says the hottest woman on earth. I always get distracted when you're around." Alphys just turned even redder in the process. "The way you talk about your anime and science gets me hot. The way you do all your weird human junk is hot."
Alphys managed a very dignified squeak. Undyne seductively slapped her tail against the bed.