Chapter Text
Barely eight years old, Byleth stared out at the horizon. Oddly empty blue eyes stayed fixed upon where the sky, painted orange by the setting sun, met the blue of the sea. The waves splashed against the rocky shore, and, in the distance, the cliffside hollowed into a cave, where the sea pooled in a gentle alcove.
Jeralt, in turn, watched his kid stare out at the sea.
Eight years of raising this kid, and he still wasn’t quite sure what was going on in that little head.
If he squinted, he could see movement near the cave. Bright blobs of colors, blurred by too-old eyes, frolicked among the sea-green waters. It was probably some kids from the nearby village playing in the ocean before the sun went down.
Jeralt looked down at his kid, noting the way those empty blue eyes tracked the movement of the brightly colored blobs in the distance. Byleth could probably see them just fine.
Maybe Byleth wanted to play with other kids, for once. All these years in Jeralt’s mercenary group, with limited interaction with other kids, it wouldn’t surprise him if this was a longing stare.
“Whatcha lookin’ at, kid?”
Byleth didn’t even blink. “...nothing.”
Never mind.
“Well, the sun’s starting to set. The crew will be wondering where we are. C’mon. Sightseeing time is over.” He switched tactics, giving up on trying to get some insight into his weird little kid. “Let’s head back.”
He held his hand out, waiting.
Byleth turned around and grabbed two of Jeralt’s fingers without a word.
As they walked away, Jeralt could feel the resistance in the little body behind him. He turned just enough to see Byleth’s head turned as far to the side as possible, still staring out at the sea.
“I’m glad you like it here enough to stare, ‘cause we’re gonna be here awhile.” Jeralt noted. “You’ll have plenty of time to come back and stare at the sea some more later, alright?”
Apparently, that was enough to sate Byleth’s curiosity(?), because the resistance Jeralt had been tugging against suddenly evaporated.
When Byleth turned back to stare one last time, Jeralt couldn’t help but laugh under his breath, amused at the sheer amount of stubbornness packed in one tiny body.
Well, he thought to himself, this is my kid, after all.
Had Jeralt turned back to look down at Byleth, he might’ve noticed the way Byleth’s empty blue eyes suddenly flooded with surprise.
Had Jeralt’s eyesight been a little better, he might’ve looked out to the sea where the kids had been playing and seen the brightly colored fish tails that disappeared beneath the waves.
---
Almost every day, Byleth went back to the seaside.
Jeralt tagged along, at first, but all Byleth did was sit on the rocks and stare out at the horizon. Eventually, he just waved goodbye whenever a little voice announced, “I’m heading out.”
There was nothing out here except fishermen and farmers. There wasn’t any large game for miles around, and the trouble Jeralt’s mercenary group had been hired to deal with was on the other side of the village, towards the trade routes.
That quiet little alcove on the sea was probably the safest place he could leave a child anyways. The water wasn’t deep enough to drown, and Jeralt had already warned Byleth away from the stronger currents farther out to sea.
Plus, that dagger on Byleth’s hip wasn’t just for show. Should any danger actually show its face, that danger would get a taste of metal right in the soft spots. Just as Jeralt had taught, time and time again.
---
About a week in, Byleth had begun to leave kid-sized boots out on the rocks a couple paces back. The water felt nice, and taking those clunky boots off felt even nicer, especially after a long day of standing beside Jeralt and walking beside Jeralt and standing around some more.
Most days, Byleth sat out on the rocks near the cove until the sun set.
Watching the water.
Waiting to see if those kids would come back.
Wondering if they had really turned into fish that day, or if that was just a trick of the light.
Maybe it was magic, Byleth mused, kicking at the vague reflection of dark blues and skin tones staring up out of the water. Magic exists. There are mages in dad’s mercenary crew. Maybe those were kid mages.
Maybe they’ll teach me some magic.
If I ever meet them.
---
Most days, Jeralt didn’t even have to go looking for his kid. Byleth usually showed back up soon after the sun set. The days that Jeralt’s voice came calling around the vicinity of the cove were the days that Byleth had fallen asleep under the warm rays of the sun.
Most days, nothing happened.
Just crashing waves, seagulls, rocks, and Byleth.
After a couple weeks of nothing, Byleth had stopped expecting the kids to show back up. At this point, the cove was just a nice place to escape to and relax for a little while.
Byleth had fallen into a routine. Show up, take off boots, sit down on rocks, dangle feet in water, alternate between staring out at the sea and staring down at the reflection in the water below, and-
“Hi!”
Suddenly, a face that was not Byleth’s reflection appeared in the water. It grinned widely up at the kid seated on the rocks above.
Spooked, Byleth’s first instinct was to whip out a dagger and brandish it in the direction of the scare.
Which was… a kid.
A kid who had clearly swam beneath the shallow water just to sneak up on Byleth.
With just their face sticking out of the water, all Byleth could really tell about the kid in the ocean was that they had bright brown eyes, freckles, and auburn hair that curled and spiraled out in a halo around their face.
“I’m Sylvain!” The kid introduced themself, sitting up enough in the water that their neck and shoulders rose above the glassy surface. “What’s your name?”
When Byleth didn’t immediately respond, Sylvain set off in a flurry of questions, undeterred by the silence.
“You’ve been looking out at the water for weeks! What did you lose? Are you looking for something?”
“Can you swim? Why don’t you get in? Why do you just sit on the rocks and stare every day?”
“Are those feet?”
“Oh, cool! A dagger! Are you going to stab me?”
Almost immediately following the dagger question, another body vaulted out of the water with a splash!
Byleth couldn’t help but notice that, despite having very normal human ears, where the normal human ears ended, the new arrival had very not normal bright blue fins extending out into sharp points on either side.
This kid’s dark hair was pulled back into a little ponytail on the top of their head, so the finned ears were obvious. Sylvain’s auburn hair was plastered to the sides of their head, covering any evidence of ears, human or not.
“Shut up!! ” A second kid screeched, slapping a hand over Sylvain’s mouth. “Who would even ask someone if they’re going to stab you? That’s how you get stabbed!”
Sylvain tried to push the other kid’s hand off of their mouth, but the other kid wasn’t budging. Actually, the other kid went so far as to try and push Sylvain back into the water, and the two set off to thrashing and wrestling each other in the shallow waters.
“Are you stupid? Are you dumb? Why do you always run your big fat mouth, Sylvain? Why don’t you ever listen to me??”
“Because I’m older! I’m in charge!”
“You are not in charge!! No one ever said you were in charge!”
As they kicked up water and dunked each other beneath the surface, two things became clear to Byleth.
One, they were not wearing any clothes. Byleth assumed, since they were bare-chested, that they were both boys. That was what Byleth knew to be true of humans that walked around bare chested. But Byleth could deal with any variation of kid, so whether the assumption was right or wrong didn’t really matter too much.
Two, they didn’t have any legs. Instead, brightly colored fish tails arced up out of the water, and wide tail fins sent water spraying every which way as they crashed back down.
“I was looking for you.”
The two boys stopped wrestling almost immediately.
“Huh?”
Byleth made sure to speak up this time, to make sure they heard.
“You asked me what I was looking for. I was looking for you.” Byleth clarified, kicking at the water with bare feet and wrinkled toes.
“Oh.” Sylvain hummed, filing that away. “Okay. Why?”
“Because you wanna stab us?” The other kid burst out, vermillion eyes fixed on the dagger still clutched in Byleth’s hand.
Whoops. Forgot about that.
Byleth sheathed the dagger. “Nope. You just… scared me. But not anymore.”
“See, Felix, I told you the human wasn’t dangerous.” Sylvain gloated and elbowed the smaller kid.
Now that the two of them had mussed up each other’s hair, Byleth could see that Sylvain sported the same finned ears as Felix, except his were bright red.
“You’re not human.” Byleth noted aloud, spurred on after hearing their use of the phrase the human.
Both boys glanced up with the same odd look sparkling in their eyes. Something like… fear.
“No.” Sylvain answered, both with words and by leaning back to lift a bright red tail out of the water. “More like, kinda human, kinda fish.”
Byleth blinked, then said, “Oh. Like mermaids. Okay.”
“Not!! Mermaids!!” Felix screeched, his little voice pitching an octave higher. “My mom’s a mermaid! We’re mermen!”
Earlier assumption confirmed, Byleth noted, boys indeed.
“Alright, alright, easy Fe, we get it,” Sylvain hid a smile behind one hand and patted the younger kid’s shoulder with the other. He looked up at Byleth and shrugged. “Felix’s older brother likes to dress him up like a princess.”
“He thinks it’s funny.” Felix grumbled. “But if I sit through it, he’ll spar with me afterwards.”
“I like to spar too,” Byleth nodded, understanding immediately. “My dad has been teaching me how to fight.”
“Cool!” Felix chirped, vermillion eyes aglow with interest. “You should play with us!”
“Do you wanna play with us?” Sylvain asked quickly, amber eyes equally bright, excited to meet a new playmate.
“Sure,” Byleth agreed. “What are you playing?”
As it turned out, they weren’t playing anything in particular. The group of kids just went along with whatever came to mind, splashing around on the rocks and in the shallow waters. And that’s what they did until the sun went down and Byleth headed back to camp.
---
That’s what they did every time Byleth met them at the cove. They played and played and played until the sun went down. Byleth didn’t get in the water much, and didn’t tend to go further than knee-deep, but the boys didn’t seem to mind.
Sylvain was a good storyteller, and Felix was wholeheartedly dedicated to whatever narrative Sylvain ended up creating, so they were pretty good playmates. Byleth usually just played whatever role Sylvain made up - which was usually a role befitting of a stoic, silent, dagger wielding child, like guard, or magic statue, or dangerous shark.
Whether it be pirates, heroes and villains, kingdoms, knights, sharks, or even the one time they’d played house, Byleth always looked forward to finding out what world Sylvain would drop the three of them into that evening.
---
Alongside the playing came a lot of talking. Byleth picked up quite a few bits of information about merpeople just by listening to Sylvain and Felix’s conversations.
Byleth was beginning to understand that mermaids weren't just pretty sea creatures. They were predators.
“Glenn’s fangs are growing in.” Felix grumbled one day. “He won’t shut up about it.”
“How cool!” Sylvain crowed, his signature giant grin beaming bright across his face. “I can’t wait until my fangs grow in.”
Byleth chose that moment to speak up. “Fangs?”
The two boys turned to their human friend in surprise.
“Do humans not grow fangs?” Felix wondered.
Byleth considered this for a moment. “I… I don’t think so. My dad doesn’t have fangs.”
And Byleth sure did know what fangs were. Jeralt’s mercenary crew had come across their fair share of creatures that wanted them dead, and plenty of those animals had fangs.
“Lemme see!” Sylvain insisted, swimming up close to where Byleth stood on the rocks near the water. “C’mere, c’mere!”
Dutifully, Byleth crouched down so that Sylvain could sit up and plant wet hands onto the sides of a stoic face, leveling honey brown eyes with vacant blue.
Sylvain was much more curious about humans than Felix. One day, he’d spent at least ten minutes just marveling over Byleth’s toes.
Today, it was human teeth that had piqued his interest, apparently.
Fingers still wet with seawater pushed Byleth’s lip up, exposing even, white teeth.
“They’re kinda dull,” Sylvain noted, nudging at rows of teeth until Byleth complied and opened up wider, “How do you cut into anything with these? Don’t the bones get in the way? Or the shells?”
Byleth’s response was pretty garbled by the fingers in the way, so Sylvain was forced to let go.
“We cook our food before we eat it. Softens it up.” Byleth explained. “Plus, I have hands. I can take the bones out before I eat.”
“Yeah, but they’re still so dull.” Sylvain argued. “Look at how sharp my teeth are. I haven’t even grown my fangs yet!”
Sylvain pulled his lip back, exposing more teeth than his grin ever had, and Byleth had to admit that he did have some very sharp teeth.
“Not sharp at all.” Felix agreed, eyeing Byleth’s human teeth in comparison to Sylvain’s.
“Sharp enough to bite someone’s finger off.” Byleth grumbled, beginning to grow tired of their teasing.
“What?” The two boys yelped in unison, surprised.
But, as per usual, Byleth didn’t elaborate.
They went back to playing.
---
There was also the time that Byleth discovered why no one had ever mentioned mermaids before.
“Oh, we try not to interact with humans much,” Sylvain explained after Byleth laid the question down. “Dad says humans are too greedy to be friends with. I think humans used to hunt us.”
“But we’re just as smart as humans!” Felix crowed, sharp teeth bared in a grin, “So they gave up after a long, long time.”
Byleth concluded that humanity must’ve forgotten about mermaids. Or, maybe they were so upset about not being able to catch them that they were pretending they didn’t exist.
Either way, it didn’t really matter to Byleth. It wasn’t like Byleth had anything to gain from telling the world that mermaids really did exist.
There was only one concern that lingered in the back of Byleth’s mind.
“You won’t get in trouble for playing with me?”
Sylvain waved a dismissive hand. “Nah.”
---
“What kind of things do you like, Felix?” Byleth wondered aloud one day.
Felix thought about this for a moment, his royal blue tail idly kicking up water behind him.
“I like… swords.” He decided. “And I like playing with my brother. And you guys.”
“Guess what Felix’s favorite color is,” Sylvain prodded Byleth, a sly grin curling his lips.
“Um,” Byleth eyed Felix’s hair and tail before guessing, “blue?”
“Why does everyone guess blue?!” Felix cried, clearly exasperated with the answer. “It’s red! And sometimes green.”
“I like blue.” Sylvain informed their human listener.
“What else do you like?”
“Hmm,” Sylvain mused, rooting around in his head for answers. “I like… red snapper for dinner. And my friends. And…” another sly grin crossed his face before he added, “And I like girls.”
Felix slapped a hand over his face, clearly exasperated with this answer as well.
“Well I don’t like girls.” Felix insisted. “Girls are boring.”
“The only girl you know is Ingrid.” Sylvain argued. “The only things Ingrid cares about are seahorses.”
“And they’re boring!” Felix exclaimed. “You’re only proving my point!”
“What about you, Byleth? Do you like girls?” Sylvain turned to their third, hoping for a tie-breaker.
Byleth shrugged. “Girls are alright. Most of the girls I’ve met told me I was weird, though.”
“You are weird.” Sylvain dismissed the anecdote. “That’s not the point.”
“Okay, well,” Byleth shifted tracks, “yeah, I like girls just fine. Boys too. I don’t mind either way.”
Sylvain seemed struck by this, as if he were having some sort of revelation only he was privy to.
“Well, I still don’t like girls.” Felix grumbled, crossing his arms over his chest. “I’d rather play with you guys. Or Glenn.”
“That’s not what we’re talking about, Fe,” Sylvain groaned.
“It’s not?” Byleth echoed, suddenly confused.
“Never mind.”
---
“Why don’t you get in the water?” Felix wondered one day.
Byleth replied with a blank stare and a monotone, “I am in the water.”
Indeed, the water pooled right at ankle height where Byleth stood.
“No, I mean like,” Felix gestured to where he and Sylvain were, where the water would be just over waist height. “Why don’t you get in the water?”
Byleth blinked, empty stare boring holes in the younger merman.
“Because I don’t want to walk back home in wet clothes.”
Sylvain rolled his eyes. “You took your shoes off, why not the rest of it? Your clothes won’t get wet on the shore.”
Byleth hesitated, little fingers lifting to grab a fistful of gray tunic.
“Sylvain,” Felix hissed, “Humans don’t just take their clothes off.”
“Yeah, but that’s for like… protection. And warmth.” Sylvain argued, as if Byleth wasn’t standing right there. “There’s nothing dangerous here, and the water’s not cold.” He held out a hand in offering, as if to coax Byleth deeper into the waters.
Still, Byleth didn’t move.
“Are you embarrassed?” Sylvain continued, pressing forward. “It’s alright, we’re not wearing any clothes either,”
“It’s not that,” Byleth interrupted, staring down at the fabric of the tunic, “it’s… My dad told me not to.”
Sylvain slumped, immediately bested by “dad said so,” but Felix wasn't deterred.
“Why?” The younger boy wondered, asking Sylvain’s favorite question for him.
Byleth shrugged and let go of the tunic. “I don’t know.”
Apparently, that was enough for them to move on and keep playing, because the topic dropped, and Byleth stayed in the ankle-deep water.
But Byleth did know why.
Jeralt had never outright said so, but the rule must have something to do with the huge scar underneath Byleth’s tunic, cutting straight down the middle of flesh and ribs. No one else around had a scar like that, at least, not of the bare chests Byleth had witnessed so far. It must be something Jeralt wanted to hide.
And Byleth was okay with that.
Byleth didn’t like looking at it much, anyways.
---
One day, Felix came to the alcove looking particularly grumpy. At least, more grumpy than usual.
“I just can’t believe Glenn asked Ingrid to be his Mate.” Felix grumbled upon being asked what was wrong. “Why Ingrid? Why not someone cool??”
“What… is a mate?” Byleth asked.
“Do you guys not have Mates?” Felix asked, seemingly shocked by this information.
“What is a mate?” Byleth asked again, forcefully punctuating every word.
“It’s like… like… when you live with someone forever,” Felix struggled to explain, “And you have kids and-”
“It’s something for people in love.” Sylvain offered, fishing Felix out, “It’s a promise to stay together.”
“Oh.” Byleth nodded, understanding. “Like marriage.”
“What,” Felix echoed, “is a marriage?”
“The same thing, I think,” Byleth explained. “It’s when two people promise to be together forever. And they have a family and a house and all that.”
“Like my mom and dad,” Sylvain helped Felix out, “And your mom and dad.”
“So Byleth’s mom and dad are Mates too?” Felix tried to connect the dots.
“I don’t have a mom.” Byleth corrected. “Just a dad.”
“Where’s your mom?”
Sylvain bopped Felix on the head for the insensitive question, but Byleth answered anyways.
“Dead, I think.”
Sylvain and Felix did that thing that they did a lot, where they looked at Byleth like an oddity. Not in the sense of being human instead of mer, but in the sense that Byleth was just… weird.
That was pretty commonplace in Byleth’s life so far.
“I don’t remember her,” Byleth continued, hoping to quell that look on their faces so they could go back to playing, “So I must have been really young.”
“Huh,” is what Felix eventually replied with.
Sylvain, ever the master of changing the subject, picked a grand topic to discuss instead.
“Who would you choose as your Mate, Fe?”
Immediately, Felix’s whole face turned as red as Sylvain’s tail. It was the first time Byleth had ever seen the younger boy truly embarrassed.
"It doesn't matter." Felix muttered, tail thrashing violently in the water- a sign Byleth had learned meant that Felix's defenses were beginning to go up.
Sylvain knew that too, which was likely the reason he smiled and changed the subject.
"I would choose Byleth, of course," Sylvain confidently informed the two of them.
"What? No!" Felix screeched, ruby red eyes popping wide open, "You can't!"
Sylvain cocked his head to the side, confused. "Why not? Because Byleth is human?"
"No- I mean-" Felix swallowed around his answer, immediately changing tactics, "Yeah! Y-yes. You can't choose a human as your Mate!"
"Sure I can!" Sylvain chirped. "What do you think, Byleth?"
Byleth looked up from the piece of coral floating on the water nearby. "Sure."
Sylvain smiled, something soft and true.
Felix threw himself backwards into the water with a loud splash!
---
Most of the time, Jeralt kept Byleth out of his mercenary work. Actually, if he had his way, it would be none of the time.
But there was only so much you could do to keep a child safe in this line of work.
"Byleth, get out of here!" Jeralt shouted, pushing back another snarling mouth full of teeth. "Run far, and don't look back!"
Byleth knew the drill.
As giant beasts tore into the cabins they'd been staying in, courtesy of the lords blocking the trade routes on the other side of the village, and Jeralt's mercenary crew fought them back tooth and nail, Byleth's place was not amidst the frenzy.
Little legs tore out of the camp, running as fast as possible towards anywhere that wasn't there.
But the movement of one unit tearing away from the pack drew the attention of the predators on the loose.
"'Lil By!" One of the mercenaries shouted, "On your left!"
Byleth's head snapped up, blue eyes alight with something primal and dangerous.
Claws and teeth filled Byleth's vision, but not for long. A quick duck out of the way sent the beast flying overhead, missing its tiny mark by a mile.
The thing scrambled to regain its bearings, monstrous red eyes darting here and there until it locked into its rapidly retreating target and burst forth once again.
Byleth ducked and weaved, zig zagging just as Jeralt always taught, running and running and running until-
Until the wide expanse of the sea unfolded before Byleth's eyes, little boots skidding to a halt against the rocky shore, spotlit by the full moon in the night sky.
The beast following close behind came to a halt too, unconcerned with its prey's escape now that Byleth was truly trapped.
It circled the child, caging its prey up against the sheer drop off of the rocky cliff and the swift currents below.
With a growl, the beast pounced,
and Byleth jumped.
Thankfully, the creature did not follow Byleth's trajectory off of the cliff and into the sea. Instead, it snarled and howled on the rocks above, mourning the loss of a good meal.
On the other hand, Byleth fought a new battle against the waves, struggling to keep a sopping wet head of blue hair above the water. Sure, Byleth could swim, but the paddling of little arms and the kicking of little legs was achieving… well, little against the monster that was the ocean.
As the currents pulled Byleth out farther, as the waves grew harsher, and as the opportunities to suck in air grew shorter, Byleth's world faded to black.
---
"...leth? Byleth? Byleth, can you hear me?"
Byleth's eyes shot open, and in an instant, there was a dagger in hand and pressed against the source of the call.
"Byleth!!" Felix screeched, gripping the wrist that brandished the dagger at his throat, "I thought you said no stabbing!!"
"Oh," Byleth blinked, finally registering Felix's face as friend instead of unidentified foe. "Sorry."
The dagger was immediately sheathed, and Byleth rolled off of Felix's prone form, freeing him.
A quick glance around confirmed they were in the alcove they always met in, though Byleth had apparently been lying half-submerged in the water until finally waking up.
"What happened?" Felix demanded. "We found you half-drowned and sinking fast just off the coast. Why were you out there? I thought you didn't swim that far out!"
"Lay off on the questions, Fee," Sylvain's voice joined the fray, unusually serious as he popped up out of the water.
"Took you long enough!" Felix shouted as he splashed through the shallow waters to the red-headed merman. “Did you get the stuff?”
“Yes, Fee, I got the stuff.” Sylvain rolled his eyes, ignoring the frenzied younger boy. “I swam as fast as I could.”
Sylvain offloaded a bundle of something green into Felix’s arms, and the two of them swam over to where Byleth laid half-submerged in the shallows nearby.
“What are you two so worried about?” Byleth wondered aloud. “Is someone hurt?”
Sylvain and Felix both rolled their eyes, exasperated.
“You, dummy.” Felix huffed. “How do you think we found you so quickly?”
Byleth looked down in surprise and came face to face with bloodstained water and a slashed calf, likely courtesy of the beast from earlier.
“Felix has a good nose,” Sylvain explained, shooting a shaky smile in Felix’s direction before pulling Byleth’s torn leg out of the water. “He probably smelled your blood as soon as you hit the water.”
Predators.
“Wow,” Byleth murmured, impressed.
Felix blushed a bright red in response to the praise, but Byleth was too busy flinching away from the salve Sylvain was applying to the open wound to notice the red on the blue merman's cheeks.
“Alright,” Sylvain announced, “Your turn, Fee.”
The boys switched places, Felix taking hold of Byleth’s leg and Sylvain swimming to Byleth’s side, and Felix began to unfurl the bundle of green clutched in his arms.
“Is that seaweed?”
Felix nodded. “It’s clean. And it’ll feel good on the wound.”
As the two boys worked to keep the injured leg elevated and attended to, Byleth began to wonder what kind of lives mermaids lived to be so used to blood and injury as children.
Not that Byleth was one to judge, considering the life of a mercenary’s kid.
“Is this too tight?” Felix asked about halfway into covering the wound. “I can’t really tell- I’ve never wrapped a leg before,” he admitted.
“It’s fine.” Byleth assured him. “Thank you.”
Felix ducked his head as he turned red again, and Sylvain snickered under his breath.
After a few moments more of working in silence by the light of the moon, Felix tied off the seaweed bandages with a flourish.
“There.” Felix announced. “All done.”
Byleth stared at the bandaged leg with empty blue eyes and slowly lowered it back into the water.
“Byleth,” Sylvain spoke up, “Are you alright?”
The only answer he received was a simple nod, but Sylvain wasn’t convinced.
“You’re shaking.” He pointed out.
“Oh,” Byleth lifted a hand out of the water and watched the way all five fingers twitched and shook. “I’m cold.”
“Easy fix,” the older boy nodded, “Felix, come here.”
Usually when Sylvain ordered Felix around, the younger boy would gripe and complain every step of the way. But not this time. Without a word, the two boys shuffled up close to Byleth, wrapping little arms around a little body to share as much body heat as possible amidst the night-chilled waters.
Jeralt's voice echoed in Byleth's ears, when someone does something nice for you, you repay them. No matter how long it takes, you repay them.
"Thank you," Byleth murmured into the night air. "I… owe you guys something."
"Nah," Sylvain shook his head, residual drops of water slinging off of his curls, "It's fine. You're our friend."
"Yeah!" Felix quickly chimed in. "We're friends! You don't owe us anything!"
Byleth gazed down at the water lapping around their waists.
Two tails, sunset scarlet and ultramarine blue, curled around Byleth's legs, protecting the wound from further damage and chasing the chill away.
"I owe you something." Byleth repeated. "Anything at all."
Felix continued to deny the request, shaking his head so fervently that the blue fins extending from his ears slapped against the sides of his head, but Sylvain fell silent, contemplative and considering.
"Well," he finally spoke up, a small grin pulling at his cheeks, "if anything's on the line, then…"
"Anything." Byleth insisted.
"Then marry me." Sylvain decided. "I would like that."
"Wh- no!" Felix immediately argued. "Not fair!"
"What, Fee?" The older merman drawled, "Too crazy for you?"
Felix bared his teeth at Sylvain in a gesture that Byleth had come to translate as stop that or I'll bite you.
"I can do that." Byleth cut through the tension building between the two boys with a simple agreement. "Shouldn't be hard."
With a shift of blue hair, Byleth turned to face Felix. "And you? You can ask for anything, too."
"Well- I-" Felix stammered, his skin beginning to blaze a bright red in embarrassment, "Then… then I want you to marry me too!!"
Byleth blinked in the wake of Felix's announcement, stunned. Meanwhile, Sylvain burst into laughter, rattling the two nearby with the shakes of his amusement.
"Felix, don't be silly, you can't-"
"I can do that." Byleth nodded. "Shouldn't be hard."
Sylvain froze, stopping mid-laugh, plunging them into silence.
"It wouldn't be hard to be with you two for the rest of my life." Byleth insisted. "It would be fun."
"Oh," Sylvain breathed out in surprise, as if Byleth had punched the sound out of him.
"Okay!" Felix nodded, resolute and satisfied. “Give me your thumb!”
Byleth’s head tilted, confusion running rampant over a usually blank expression, and Sylvain’s eyes blew wide.
“You can’t be serious, Fee,” he sounded winded, as if someone had punched the air right out of him.
“You weren’t?” Felix returned, holding Sylvain’s stare with way too much ease for someone so young.
“I-” Sylvain swallowed hard, then rearranged his features into something more resolute, “I was.”
“Will someone tell me what’s going on?” Byleth sighed, all too used to being talked around as the only non-mer in the group.
“Right,” Sylvain warbled, still nervous, “Felix wants to make a blood promise. An exchange of blood between two people to seal a promise. Mates do it when they promise themselves to each other.”
“So… it’s a big deal.” Byleth quickly figured out the source of Sylvain’s hesitation. Sylvain and Felix both nodded.
Byleth thought about it, as much as an eight year old could consider promising one’s self to another, and came to a decision.
“Sure,” a thumb brandished in Felix’s direction made red eyes light up in delight, “Go ahead.”
Felix took Byleth’s hand in both of his and brought the offered thumb to his mouth. A press of a sharp canine into skin easily drew blood to the surface.
“Your turn,” Felix insisted, pushing his thumb into Byleth’s face.
Byleth had to think for a moment, fully aware that human canines weren’t going to have the same effect as mer-canines, and eventually pressed both the blade of a dagger and a gentle kiss to Felix’s thumb in return.
Then, Felix pressed their cut thumbs together, exchanging blood and spit to seal the promise.
“My turn,” Sylvain piped up as soon as their thumbs separated. “Me too.”
Sylvain repeated the process, as did Byleth, and the redhead seemed incredibly pleased when their bloodied thumbs pressed together to seal the deal.
“Now give me yours,” Sylvain turned to Felix, a hand extended towards the younger mermaid.
“Wh- but I- Sylvain, you can’t-” Felix stammered, beginning to go all red in the face- which told Byleth that he really didn’t have any problem with the request at all.
“You’re the one that made me promise that we wouldn’t die without each other,” Sylvain reminded him, exasperated by his hesitation, “Now give me your thumb!!”
Outed and mortified, Felix extended his thumb without any further argument and even bit Sylvain’s in return.
Once their thumbs pressed together, the lingering tremors wracking Byleth’s tiny frame disappeared altogether, as if even Byleth’s body agreed to their decision.
As their conversation ended, Byleth began to wind down and nearly fell asleep multiple times -- only to be woken up by Felix shuffling into a more comfortable position or Sylvain humming to himself to pass the time.
The next time that Byleth was close to drifting off again, Felix’s voice tore the veil of sleep away.
“Should we… should we ask King Lambert for help?”
The question was clearly aimed at Sylvain, so Byleth pretended to still be asleep.
“I mean,” Felix continued, nerves edging his tone, “There’s not much more we can do. And if Byleth is all alone now, then-”
“Let’s just wait a little longer.” Sylvain quietly replied, clearly just as worried. “It’s only been a couple hours since we got here anyways.”
---
With the beasts quelled and the responsible lords in custody, Jeralt’s mercenary crew finally had a chance to relax.
Well, everyone but Jeralt could.
“Where’re ya headed, boss?” One of the crew members called after him as he headed off into the night.
“Gotta find the kid.”
“Fuck!” Another mercenary shouted in horror. “‘Lil By was in big trouble! One of those beasts was after the poor kid!”
Everyone in the nearby vicinity straightened as they watched Jeralt shift into Protective Dad Mode.
“Carson! Jeremiah! Head east. Search the forests.” Jeralt barked. “Mimson and Shalt, head north into the village. Ask around.”
“On it boss!” Came the responding chorus of voices.
“Deydra and Fennel, stay here in case Byleth comes back while we’re gone. And Kingston, you’re with me.” Jeralt jerked a finger over his shoulder, pointing south, in the direction of the ocean. “Let’s head out.”
---
To be completely honest, Jeralt wasn’t one hundred percent certain that he’d find Byleth at the seaside. It was just a hunch.
“Boss.” Kingston called for Jeralt as he kneeled to inspect the dirt. “Claw marks. Tracks.”
Jeralt eyed the marks in the dirt, then glanced over to the cliffside nearby. “Shit.”
Kingston nodded in agreement.
“Follow the tracks. Make sure there aren’t any beasts left over to terrorize the village.” Jeralt commanded. “I’ll search the shoreline to see…”
To see if the kid has washed up anywhere.
“On it, boss.” Kingston set out immediately, his hulking frame quickly fading into the night.
Jeralt turned back towards the ocean with a sigh.
Byleth… please be okay.
---
Byleth had long since fallen into a fitful rest, too tired to fight the pull of sleep any longer.
Distantly, something… someone was… calling.
“..leth? Byleth?”
Byleth could only groan and try to roll over, but even the rolling over part didn’t pan out.
“Byleth?”
Vaguely, Byleth felt cold all of a sudden- which was weird, because… wasn’t Sylvain… and… and Felix…
“Byleth! Byleth, can you hear me?”
The sound of water splashing filled Byleth's ears, and in one fell swoop, warmth flooded Byleth's body.
"Cold," Byleth mumbled, turning to bury a frozen nose into the source of the heat.
"I've got you, kiddo," Jeralt's voice became audible, rumbling through his chest and into Byleth's. "Let's get you warmed up."
---
Later, when Byleth was fully conscious and no longer half-frozen, Jeralt asked who had supplied the medical care before he got there.
Empty blue eyes stared into the fire, little fingers twisted into newly dried clothes.
At first, Jeralt didn't think he was going to get an answer.
Then, Byleth's eyebrows twisted into a knot -- probably the most emotion Jeralt had ever witnessed from his stoic child.
"My fee… my fan… my…"
"Describe it to me," Jeralt offered, eager to find out what could possibly evoke such a reaction in his kid.
"What's the fancy word for… for…" Byleth struggled, fingers clenching into frustrated fists, "When you're going to be married? But not yet?"
"...Engaged?"
"No," Byleth answered with a shake of the head, "The fancy word for the person you get engaged to."
"What, a fiancé?" Jeralt supplied, almost laughing at the thought of his Byleth engaged.
"Yes," Byleth nodded, eyebrows relaxing into their usual slack position. "My fiancés bandaged my leg."
"Your what?!"
---
After clearing the village of beasts and bringing down the corrupt nobles behind it all, Jeralt's mercenary crew began to pack their bags. With the job done, there was no reason to stay any longer. It was time to move on to the next job.
In the chaos of packing up and moving out, Byleth slipped away from the camp and headed for the ocean one last time.
It was a little earlier than their usual meeting time, but Byleth wasn't surprised to find the two splashing about in the shallow waters regardless.
"Byleth!" The two greeted the newest arrival with bright smiles and the splashing of brilliantly colored tail fins.
"You're just in time!" Sylvain crowed. "We were just about to encounter the beautiful yet vicious sirens of the Far Sea in our adventures. We'll need your-"
"I'm leaving." Byleth interrupted.
The alcove fell silent. Sylvain's grin dimmed considerably and Felix's lips pulled into a tight line.
"Everyone's packing up." Byleth continued. "We'll head out by sundown."
"Why?" Felix demanded with a start, kicking up water as he lurched forward.
"Because we did what we were hired to do," Byleth echoed Jeralt's earlier explanation, "And the village won't provide for freeloaders."
Sylvain wasn't speaking- which was unusual, for him- and Felix looked positively devastated.
"You don't have to leave!" Felix insisted, swimming close enough to wrap an ocean drenched hand around Byleth's ankle. "You could… you could stay with us!"
"Fee," Sylvain murmured as he shook his head, "We can't do that."
"I can't breathe underwater like you can." Byleth agreed. "I can't."
"But-!" Felix argued, his tail angrily slashing through the shallow water beneath them, "That's not- that's not fair!"
Sylvain seemed to agree, but he didn't say anything else on the matter.
The two boys seemed truly dejected to see their friend leave (and potentially never come back).
Being a mercenary's kid, Byleth had already experienced plenty of goodbyes.
It truly wasn't fair, to make friends and disappear shortly after, but it was the only life Byleth knew.
Fortunately, being so experienced in goodbyes made navigating moments like these a little easier.
"I brought you guys something." Byleth changed the subject- and it snagged both of the merboys' attention, so the diversion seemed to work. "Something to remember me by. If you want it."
"I do," Felix nodded eagerly, tugging impatiently at Byleth's ankle. "I won't ever forget you. Even without a gift." He promised.
On the other hand, Sylvain didn't react. Not even a little bit.
"Here," Byleth handed Felix a little wrapped pouch. "That's my dagger."
"R-really?" Felix stared at the package, starry eyed. "I can have this?"
"Something to remember me by." Byleth insisted. "And Sylvain,"
"I don't want it." He cut Byleth off, expression stormy and petulant. "If you're leaving, I don't want anything from you."
"Sylvain," Felix whined, turning around with a huff of dissatisfaction, "Don't be mean."
"It's alright," Byleth shoved the gift deeper into fabric pockets, hiding it away. "I get it."
"You don't get it!" Sylvain glared daggers at Byleth's tiny form, his tail sending up a spray of water to punctuate his outburst. "You don't get it at all!"
To Byleth and Felix's surprise, Sylvain turned on a dime and dove into deeper water before taking off like a shot into the afternoon waves.
Gone, without even a goodbye.
This was something Byleth would expect from Felix on any given day, but for Sylvain to act like this… well, Byleth simply didn't know what to do in response to that.
"Here," Felix offered up a hand, "give it to me."
Byleth simply stared down at the merkid half submerged in the water below.
"The gift," he insisted, "I'll give it to Sylvain."
"He doesn't want it." Byleth reminded him.
Felix dramatically rolled his eyes in the way he'd recently begun to do in response to literally any inconvenience.
"Sure he does. I'll give it to him."
Byleth looked between Felix's outstretched hand and the waves Sylvain had shot off into as if something had been chasing him.
For the first time in Byleth’s short life, a tight bundle of feelings tied themselves in a knot in the pit of Byleth’s stomach. Weird, unfamiliar feelings, like… longing, guilt, and hurt.
Silently, Byleth dropped a hand-braided necklace into Felix's hand. Felix dangled the gift in front of his nose in order to better inspect it, and crimson irises lifted up to meet empty ocean blue.
"Did you make this?" Felix asked, voice pitched high in surprise.
Byleth nodded.
"Sylvain likes things like this." Felix noted, admiring the single shell woven in with the cord. "He'll like it."
"I hope so." Byleth murmured.
Felix tucked the necklace into the pouch with the dagger, then turned and opened his arms wide in Byleth's direction.
"Come here," Felix announced. "You're supposed to hug before someone leaves."
"Merfolk tradition?" Byleth asked, familiar with the two boys' supposed to's and we always's - ever careful not to say mermaid instead of the general merpeople or merfolk, since it pissed Felix off so much.
Felix confirmed the guess with a nod and shook his arms expectantly, gesturing Byleth in closer.
Byleth shucked off socks and boots and stepped into the water for the first time that day.
"Lower," Felix whined, "Merfolk don't stand."
Byleth dutifully rolled up pant cuffs until it was safe to kneel in the water without getting too wet.
As soon as Byleth was in range, Felix lunged forwards, wrapping little arms around an equally as little body and squeezing tight.
Byleth squeezed back. "Goodbye, Felix. I'll miss you."
The younger boy squeezed tighter for a second before leaning away. But before Byleth could stand back up, Felix pulled on little shoulders and planted a kiss on Byleth's cheek with a resolute mwah!
Immediately flustered by his own actions, Felix reeled back and swam a couple paces away, nearly hiding his face in his hands out of sheer embarrassment.
"Another tradition?" Byleth wondered with a curious tilt of the head while standing once more.
Felix didn't answer the question, but he did say, "I'll miss you too," before swimming away and disappearing into the ocean just as Sylvain had.
Leaving Byleth alone in the alcove.
---
The only question Jeralt had when Byleth eventually turned back up was,
"Where's your dagger?"