Chapter Text
The ocean was too wide. Too blue. Too open.
Sun clung to the reef’s edge like it might drift away without him.
He blinked into the watery haze. No glass between him and the world anymore. No crowds tapping on the enclosure. No children pointing. No scheduled feeding time. Just... real ocean.
Cold.
Vast.
Loud.
Something shifted in the murk beyond him.
Sun straightened, gills fluttering with anxious excitement. Maybe it was another Mer? A guide? The humans said there were others like him out here. Someone would show him around, right?
The shape glided closer. Streamlined. Elegant. Silvery-blue.
A Siren.
But Sun didn’t know that. He only knew the figure was beautiful.
“Hi!” Sun chirped, raising a webbed hand in greeting. His voice came out bubbly and wrong under the water, but the sentiment was clear. “I'm Sun!”
The stranger paused, hovering in the water like a shadow stitched to the sea itself. His black-scaled arms flexed slowly, claws half-bared at his sides. Teeth gleamed from behind his closed lips, far too sharp to be comforting.
Moon narrowed his eyes.
This Mer—Sun, he said?—was beaming. Unarmed. Wide open. No scent of fear in the water, only curiosity and trust.
That was... unnatural.
Sirens weren’t supposed to hesitate, especially when their prey smiled at them.
“Zha'kai,” Moon muttered under his breath in the old tongue. Stupid fish.
Sun tilted his head. “Was that your name? That’s a pretty name!”
Moon froze.
He tried again, slower this time, enunciating with subtle clicks and body posture—communication through ripple and movement. It was the way ocean folk spoke, the true language of the sea.
But Sun just blinked, then smiled brighter. “I don’t know what you’re saying, but it sounds super cool!”
Moon recoiled slightly. What the abyss was wrong with him? Even the simplest signals—danger, warning, predator—got no response. This Mer wasn’t just fearless. He was clueless.
He’d never been taught.
Moon narrowed his eyes further. “You... don't understand me,” he tried, this time shaping his lips around clumsy surface-lander syllables. His voice was raspy, cracked from disuse. Sirens didn’t usually speak above the waves. It hurt to force the words out.
Sun gasped. “You can talk! Oh, thank god—I thought I was gonna be stuck miming for the rest of my life.”
Moon opened his mouth. Closed it. The kill would’ve been easy. So easy.
But Sun swam closer instead, hands clasped together excitedly. “Okay, okay! So—what’s your name? Can you show me where the others live? Or like, what do you eat? Do you guys have parties down here or—”
“You should not be here,” Moon interrupted sharply.
Sun blinked. “Why not?”
“I’m supposed to kill you,” Moon said flatly.
Silence stretched between them.
Sun tilted his head again. “What?”
Moon stared. Sun stared back.
Moon swam a slow circle around him. No reaction. No alarm. Just that dumb, innocent grin.
He came back around to face him. “You don’t... understand, do you?”
“Nope,” Sun chirped. “But I like your eyes! They’re spooky.”
Moon flinched. “You think I’m trying to be friends?”
“Well... aren’t you?” Sun asked. “I mean, you swam up to me and didn’t eat me or anything. That’s friend material in my book.”
Moon’s jaw dropped slightly.
Sun leaned closer. “Wait. Did you say something about killing me?”
Moon blinked once. Then again. Slowly.
Then he burst out laughing. A strange, soft, disbelieving sound—more of a breathless exhale than amusement.
This Mer was going to die.
Not by his claws.
By sheer stupidity.
Or—no. No, not stupidity.
Naivety.
There were no scars on his body. No hardened instincts. No knowledge of the warning signs. Sun floated like a creature raised in light and safety, not in the harsh dark waters where predators smiled before they struck.
Moon’s claws slowly retracted.
He should kill him.
But something in Sun’s gaze made it hard.
Not because he was beautiful.
Not because he was helpless.
But because he was the first creature to ever look at Moon like he was something other than a threat.
Sun drifted a little closer, then paused, wringing his hands nervously. “S-So... do you, uh... want to maybe show me around? Just a little? I’ll be super quiet. And polite. And I won’t touch anything.”
Moon stared at him. For a long, long time.
And then, without a word, he turned and began to swim.
Sun's tail perked up in delight. “Is that a yes? Are we going somewhere? You do want to be friends!”
Moon didn’t answer. He couldn’t.
His mouth was set in a line too tight for words.
He didn't know if he was sparing Sun...
...or luring him deeper.
The deeper they swam, the darker the water became.
Sun trailed behind Moon like a puppy—tail flicking too fast, eyes drinking in every glowing coral bloom and school of darting fish with wonder. His hands brushed the reef walls with reverence. His fingers lingered on fronds of seaweed, like even that was a miracle.
Moon hated how quiet he was being.
Not because Sun talked too much—he absolutely did—but because Moon hadn’t told him to shut up. Hadn’t growled. Hadn’t clawed at him. Hadn’t even flashed a warning fin.
What was wrong with him?
Sun finally caught up, hovering just beside him. “Sooo... where are we going?”
Moon didn’t answer.
Sun frowned, just a little. “You don’t talk much, huh? That’s okay. I talk enough for both of us.”
He laughed to himself like he’d made the best joke in the world.
Moon looked away.
They passed the jagged mouth of a crevice—long, dark, and narrow. It pulsed with cold water and echoed with the remnants of distant songs. Siren territory. Real sirens.
Moon hesitated.
Sun, of course, swam right up to the entrance.
Moon shot forward and grabbed him—not gently. His claws dug into Sun’s arm just enough to stop him cold.
“Don’t,” Moon said, voice low.
Sun blinked at him. “What’s wrong?”
Moon didn’t answer. He was listening. Watching. The reef was still. No movement. No sound. But he knew the others were close. He could feel it in his bones.
“You can’t go in there,” Moon finally muttered. “They’ll smell you.”
“Smell me?” Sun asked. “Like... for fun? That’s weird.”
Moon’s fingers tightened.
Sun’s smile faltered. “…Orrr not for fun?”
Moon stared at him, really stared.
“…You really don’t know what you are,” he said quietly.
Sun furrowed his brow. “I’m a Mer. They told me that at the aquarium. I think. They weren’t super sure. I kinda just showed up in one of their pipes when I was a baby.”
Moon didn’t move. “…You were raised by humans?”
Sun nodded proudly. “Yeah! They fed me through a little chute and gave me toys! One of them let me play with her phone sometimes.”
Moon stared at him like he’d grown a second tail. “You don’t know anything, do you?”
“Well... not ocean stuff,” Sun admitted. “But I can tell you the alphabet. Want to hear it?”
Moon let go of him.
Sun didn’t swim away.
“…Why haven’t you tried to eat me?” Moon asked flatly. “You’re alone. Defenseless. Your scales are too soft. You’re slow. You didn’t even flinch when I said I was supposed to kill you.”
Sun tilted his head again. “Wait, was that real?”
Moon gave him a look.
“Oh. Huh.” Sun looked down at his own arms, flexing one. “That’s kinda rude. I mean, I wouldn’t hurt you.”
Moon’s face didn’t change, but his throat bobbed as if he were trying to swallow something.
“…You’re not like me,” Sun said softly. “Are you?”
Moon didn’t answer.
Sun leaned a little closer, voice gentler this time. “Your teeth are sharp. And your eyes glow. You move like a shadow. You’re really fast. And you talk weird. Are you—like—another kind of Mer?”
Moon met his gaze. “…No.”
Sun blinked. “Then what are you?”
Moon didn’t answer.
Instead, he turned and started swimming again. “You want answers? Then follow me. But stay close. If they catch your scent, I won’t be able to protect you.”
Sun's tail flicked nervously. “…But you will try, right?”
Moon didn't look at him. “Just swim.”
Sun followed.
They reached a shallow trench nestled between two coral cliffs. It was a quiet place—no song echoes, no distant trails of blood. A secret place.
Sun drifted lazily through the kelp, smiling again now that the tension had dropped. He swirled in a circle, letting the water lift him.
“It's pretty here,” he said.
Moon hovered just above him, arms folded across his chest. “Why are you so calm?”
Sun opened his mouth, then paused. He floated upright and looked at Moon with complete sincerity.
“…Because you didn’t kill me.”
Moon blinked. “That’s all it takes?”
Sun shrugged, smiling sheepishly. “I mean... yeah? You could’ve. But you didn’t. So you’re probably a good person. Or fish. Or guy. Or... whatever.”
Moon didn’t know what to say.
So he said nothing.
Until—
“…What if I changed my mind?”
Sun paused. “About being friends?”
Moon’s face hardened. “About killing you.”
Sun was quiet for a long moment. Then, gently, he asked: “Would you feel bad afterward?”
That threw Moon off more than any scream could’ve.
He looked away. “You shouldn’t care.”
“I kinda do,” Sun admitted, voice light. “I like your voice. And your eyes. And the way you get all grumbly when I talk too much.”
Moon’s jaw clenched. “Stop talking.”
Sun smiled. “Okay.”
And then he floated a little closer.
Moon didn’t stop him.
They found a quieter place after that—an overhang in a rocky reef wall, hidden behind thick strands of swaying seaweed. Safe, for now.
Moon paced in tight circles outside the mouth of the alcove, his fins twitching in irritation. Every time he looked at Sun, sprawled across a patch of sand like it was a hammock, he felt his brain short-circuit.
Sun was smiling again.
Of course he was.
Moon bared his teeth and looked away.
“You’re mad,” Sun said, propping his chin on his hands. “Is it because I said her singing was weird? ‘Cause I stand by it.”
Moon didn’t respond.
Sun sighed and flopped back. “Okay, listen, I know I didn’t get the whole magic singing thing, but you gotta admit—it’s kind of cool that I didn’t fall for it, right?”
Moon spun on him.
“Cool?” he snapped. “You almost got dragged into the deep, and you called it opera! That wasn’t singing. It was compulsion. It’s magic, not a performance!”
Sun blinked. “Well, I thought it needed better rhythm.”
Moon stared at him.
Then, slowly, something dark and clever crept into his eyes.
“…Fine,” he muttered.
Sun perked up. “Fine what?”
Moon turned away, folding his arms. “I want to try something.”
“Oh?” Sun pushed himself upright. “What kind of something?”
Moon didn’t answer.
He took a slow breath, closed his eyes—and began to sing.
But this wasn’t like the other siren’s voice. Moon’s was lower, smoother. It slid through the water like silk and shadows, curling in delicate ribbons around them both. It wasn’t threatening. It was... haunting. Intimate. Like a secret whispered directly into your bones.
Power coiled beneath each note—ancient and heavy. The kind of sound that could melt fear or sharpen it.
It would have dropped a trained Mer to their knees.
It should have brought Sun under in seconds.
But instead—
“…Are you okay?” Sun asked gently.
Moon’s eyes snapped open mid-note.
Sun had one brow raised, a little wrinkle between his eyes. “You sound... kind of constipated. Are you trying not to fart or something?”
Moon choked.
His song cut off instantly.
“I mean,” Sun continued, tilting his head, “you’ve got this really dramatic face and the sound’s all ‘oooohhhh—eeehhhh—grhhhhh,’ like you’re trying to summon a ghost with indigestion.”
Moon looked like he was about to explode.
“That was a siren’s call,” he snapped. “You’re supposed to freeze. Or at least shut up. Not critique it like a sea witch judge.”
Sun winced. “Oh. Sorry.”
A pause.
“…You kinda went flat at the end though.”
Moon screamed internally.
He turned and slammed his head against the rock wall.
“Okay!” Sun said quickly, swimming over. “Okay, okay, that was mean. I didn’t mean it! You were really, um, moody! Very... echo-y!”
Moon groaned against the rock.
Sun hovered beside him like a guilty child. “Hey. Don’t be mad.”
“You’re immune,” Moon mumbled into the stone. “You’re actually immune. This shouldn’t be possible. Not even sirens resist other sirens. You shouldn’t—this shouldn’t—”
“You okay?”
“No,” Moon growled.
Sun reached out and patted his shoulder. “Well... I liked it anyway. Even if I didn’t fall into a trance or whatever. Your voice is really... you.”
Moon went still.
He slowly turned his head, scowling—but softer now. “…Me?”
Sun nodded. “Like—cold, spooky, and makes me feel kinda weird in my stomach.”
“…Is that a compliment?”
“I think so?”
Moon stared at him for a long moment. And then, very quietly, laughed.
Sun lit up like a jellyfish. “See? You do like me.”
Moon rolled his eyes. “You’re like a barnacle. Impossible to remove and always talking.”
“But cute!”
Moon didn’t respond.
He just swam deeper into the alcove and muttered over his shoulder, “Come on. You’ll get yourself killed if you’re not attached to me.”
Sun followed. “So, we’re, like... buddies now?”
“More like I’m babysitting a singing-immune idiot who thinks I’m constipated.”
“Besties it is.”
Sun had been acting weird all morning.
Which, for most people, might mean quiet and twitchy. But for Sun, it meant humming louder than usual, poking around coral beds with suspicious focus, and disappearing behind rock outcrops with a mischievous little grin every five minutes.
Moon had no idea what he was doing.
He didn’t care.
He didn’t.
He told himself that a lot.
He just happened to keep glancing back over his shoulder to make sure Sun hadn’t wandered into a kraken’s den or started a conversation with a venom eel again.
“Moon!” Sun chirped, finally darting back over, hands behind his back and tail flicking like an excited seal. “I made something for you!”
Moon narrowed his eyes. “Why.”
Sun beamed. “Because you’re cool! And I like you!”
Moon’s expression didn’t change. “You also said I sounded like I had a gastrointestinal emergency yesterday.”
Sun giggled. “Exactly! Friendship~!”
He brought his hands forward and offered the “gift.”
Moon stared.
It was a little bracelet—if you could call it that—made of sea glass, bits of bright shell, and tiny braided seaweed cords. It was messy, knotted in weird places, one of the shells was cracked, and it was obviously made by someone who had zero clue what he was doing.
It was hideous.
It was... kind of adorable.
Sun held it out proudly. “I made it from stuff I found this morning! Took forever to get the seaweed to stop slipping, but look! It stretches!”
Moon’s throat felt dry.
“You...” he said slowly, voice low and oddly rough, “...made this. For me?”
Sun nodded. “Uh-huh! You can wear it on your wrist! Or your fin! Or your tail—wait, do sirens do accessories? I never asked.”
Moon didn’t answer.
Because his brain had just imploded.
See, in human culture, gifts were sweet and sentimental.
In siren culture?
That was a courtship offering.
Handmade. Offered from palm to palm. Materials gathered by the giver. Given directly to the chest or wrist.
That was mate language.
That was I want you as mine.
Moon blinked once.
Then again.
Then he just froze.
“Moon?” Sun said after a moment. “Are you okay?”
“You gave me a mating bracelet,” Moon whispered, in a tone of sheer horror.
Sun tilted his head. “A what now?”
“This—” Moon lifted the mess of shells like it was radioactive, “—this is siren courtship. You—this—You’re literally asking to be my mate.”
A pause.
“…Oh,” Sun said. “Well. That explains the weird vibe I got when I handed it to you.”
Moon stared at him.
Sun scratched the back of his head. “Okay, BUT in my defense, no one told me making a friendship bracelet underwater would be a proposal. I just thought you’d like shiny things!”
Moon’s claws twitched.
His gills fluttered.
His heart was fluttering, and that was worse.
“Take it back,” Moon said quickly, thrusting it toward him. “You don’t know what you’re doing. You can’t give this to people—sirens kill each other for less!”
Sun looked at the bracelet, then back at Moon.
And smiled.
“Nah,” he said cheerfully. “I like you. You can keep it.”
Moon’s pupils dilated. “Sun.”
“What? It’s cute!”
“You—I am not cute!”
“You are when you get all flustered like that.”
Moon nearly screamed.
Instead, he turned and slammed his head against a nearby boulder again, letting out a long groan of defeat. “You’re going to kill me. You are going to kill me faster than the entire reef put together.”
Behind him, Sun laughed.
“I can make another one if you want!”
“Do not.”
“What if I make you a matching necklace?”
“I swear to the trench—!”