Archive of Our Own ^beta

Moon did not float.

He fell.

Not through water — through darkness. Endless and suffocating, not even the trench had ever been this cold.

It was the in-between. The space where voices twisted into echo, where sirens returned when they lost themselves.

Where things were forgotten.

And yet…

A voice echoed in the distance. Soft. Familiar. Warm.

“...Don’t you dare die on me.”

Sun clutched Moon’s body tightly, shielding him behind a curtain of coral and frantically glowing jellyfish. The reef was chaos around them — mers fleeing, sirens snarling, ancient songs cutting through the water like blades.

Moon’s breathing was shallow. His eyes closed. His chest was marked with slashes that bled light.

Sun didn’t care that he was terrified. Didn’t care that Moon was supposed to be the monster.

He wasn’t.

He was the only one who’d stayed.

The only one who’d chosen not to sing.

“Come on,” Sun begged, pressing his hands against Moon’s chest. “You can’t leave now. Not after everything. Not after that stupid song you broke yourself singing.”

No response.

Sun choked. He felt the sob rise in his throat, bitter and ugly.

“Why’d you protect me?” he whispered. “Why would you do that?”

A faint pulse flickered under his palms.

Sun’s heart jumped.

“Moon?”

Moon’s eyes cracked open — just a sliver. Glowing dimly, like twin stars at the edge of collapse.

Sun nearly cried from relief. “You stupid, brave fish.”

Moon tried to speak, but coughed instead — bubbles spilling from his mouth. He grabbed Sun’s wrist, weakly pointing toward the reef’s core.

The mers. The others.

“They’re still fighting,” Sun whispered. “But without you, they’ll—”

Moon shook his head.

Then pointed at Sun.

At his own chest.

Then curled his hand like a closing fist.

You.
Lead them.

Sun’s mouth opened, stunned.

“You want me to…?” He hesitated. “But I’m not—”

Moon pressed a claw to his lips. Then to his heart.

You are.

Sun didn’t think.

He moved.

With Moon weakly floating behind him, he rose out of the coral like the morning sun itself — light bursting from his skin, glowing so brightly it blinded the sirens around him.

For a moment — just a moment — they hesitated.

He used it.

Sun sang.

Not like a siren. Not a weapon.

A song of light.

Of reef and warmth and laughter. Of coral gardens and stupid crab jokes and dancing with dolphins. A song of everything that Moon had never had — but chose to protect.

And for the first time…

Some of the sirens paused.

One of them — young, unsure — blinked slowly, the glow in her eyes flickering.

The lead siren shrieked.

She launched toward Sun, claws extended, venom blazing.

Moon moved.

Even bleeding, even broken — he flared to life, intercepting her mid-charge.

They clashed, siren against siren — but Moon didn’t sing. He held her, locking her in his arms, wrapping his tail around hers like chains.

Then he dove.

Straight into the trench.

Dragging her with him.

Sun screamed after him. “MOON!!”

No answer.

Only stillness.

Only quiet.

Only bubbles.

Hours later, the reef slowly began to heal. The remaining sirens scattered like broken shadows. The mers gathered in the shallows, shaken but alive.

Sun hovered alone at the edge of the reef, staring into the trench.

Waiting.

Not moving.

Not singing.

Just waiting.

And then—

The water shimmered.

A shape broke the surface.

Tattered fins. Pale scars. Glowing marks.

Moon.

Alive.

Barely.

But alive.

Sun surged forward, grabbing him, dragging him up into the light, cradling him with both arms.

Moon blinked.

Sun smiled, trembling. “I’m gonna kill you for doing that.”

Moon smirked — just barely — and croaked,

“Worth it.”

Moon was not used to warmth.

Healed coral. Gentle waters. Sunlight. Hands that touched without fear.

Sun stayed close, always — helping him float when his strength faltered, guiding him through the reef with small, careful nudges, like Moon might break if pushed too hard.

Moon didn’t know how to accept that kind of kindness.

But Sun kept offering it anyway.

Day by day, piece by piece, Moon stopped flinching.

He even learned how to laugh.

Well—kind of.

It came out more like a low purring hiss, bubbles spilling from the corners of his mouth, but Sun beamed every time.

“See? That’s your laugh,” he’d say, “It’s awful. I love it.”

Moon rolled his eyes every time.

But deep down, something new was blooming. Something fragile. Something dangerous.

Not a siren’s desire.

Something closer.

Something like love.

Sun started bringing Moon bits of reef glass, weaving it into strands with kelp — not gifts, he claimed. Totally not courtship things. But Moon wasn’t stupid.

He’d seen mers give trinkets before. He knew what it meant.

Still… he never gave them back.

Sometimes, he even wore them.

The reef slowly began to accept him. Hesitantly. Not fully.

Some mers turned away when he passed. Some whispered.

Some stared at his scars and glowing marks like reminders of blood.

But Moon stayed. And protected. And watched.

And Sun never left his side.

They were happy.

For a time.

Until the sky cracked.

One morning, the reef’s calm was shattered by the sound.

A deep, metallic hum. Unnatural. Alien.

Moon froze. Sun bolted upward.

And from the surface — shadows fell.

Massive machines with legs and glass eyes. Lights that cut through the sea like knives. Human divers wrapped in slick metal skin. Floating cages. Sonar pulses.

And then:

A net.

Moon’s instincts screamed. Sirens and humans were ancient enemies. Their blood soaked the trench. He lunged to protect Sun, pushing him behind coral.

But Sun grabbed his wrist. “No—wait!”

The humans didn’t attack right away.

They were looking.

Watching.

Recording.

And when one pointed at Moon — with wide, stunned eyes — the others froze.

Moon realized too late what they saw:

Not just a siren.

But a siren beside a mer.

Not fighting. Together.

A secret worth stealing.

The cage came down.

Sun tried to shield Moon.

Moon threw him aside and took the hit.

Bars snapped around him like teeth, laced with sharp sonar bursts. His glow flared in panic — he thrashed, snarled — but it was no use.

They were pulling him up.

Sun screamed, slammed into the bars — biting, clawing, desperate.

“NO! NO! LET HIM GO!”

But the humans only stared in awe.

And in the distance…

One of them smiled.

Moon’s gaze locked with Sun’s through the bars.

His claws gripped the metal, still sparking with sonar.

Sun’s hands covered his. Shaking.

“I’ll find you,” Sun whispered, tears blurring his glowing eyes.

Moon touched his forehead to the bars, breathing his last words before the cage vanished above the reef—

“Mine.”

Moon had never known dry.

Not truly.

Not like this.

The tank was enormous by human standards — sealed in glass thicker than any sea-smooth stone, lit with buzzing fake lights, cold filters pushing in sterilized water.

To them, he was a marvel. A myth. A specimen.

To Moon?

It was a cage.

A coffin.

He hovered in the tank’s center, coiled but motionless, glowing softly like a dying ember. Chains of sonar pulses rang around the top and base — low and constant, a threat. Enough to keep his siren instincts buried beneath exhaustion and pain.

He didn’t try to sing.

Not yet.

They were waiting for that. He could see it in their giddy, hungry stares through the glass. Scientists, researchers, collectors.

The ones with badges whispered words like:

“Unnatural pairing…”

“Never documented coexistence…”

“Merfolk will want him back — bait, maybe?”

He didn’t respond.

Didn’t scream.

Didn’t beg.

But his claws twitched.

Because somewhere below the surface, Sun was burning.

And Moon could feel it.

Sun was burning.

With rage. With fear. With guilt.

The reef was in chaos.

Some mers wanted him banished — how dare he bring a siren into their waters?

Others whispered of legends — of sirens who turned from blood. Of fate.

But Sun ignored them all.

He only listened to the waves.

To the current that had once carried Moon to him.

And now carried nothing.

He could feel the missing.

Like a part of his chest had been scooped out and filled with ice.

So he dove.

Deep.

To the edge of the trench.

And sang.

Not the way sirens do.

Not to lure.

But to call.

Moon’s head jerked in the tank.

The humans noticed the flicker in his glow, the twitch in his tail.

They scrambled for recording tools.

They didn’t hear it.

But Moon did.

Far beneath the steel and salt, across miles of cable and pressure and pain — he heard it.

A song.

His song.

From Sun.

Calling.

Reaching.

“I’m coming.”

He struck.

The scientists didn’t see it coming — they thought he was docile, stunned. Tame.

They’d forgotten what sirens are.

Forgotten he was from the depths.

The sonar chains cracked as his glow flared violet, his song bubbling just under his breath — not full volume, not enough to kill, but enough to stun. Enough to break glass.

He screamed once — a single syllable:

“SUN!”

Then the tank shattered.

Sun shot upward.

Water churned. Machines lit the sea like lightning. Spotlights speared the reef.

And from the center of the chaos — bleeding, glowing, furious —

Moon fell from the sky.

Straight into Sun’s arms.

They didn’t speak.

Didn’t need to.

Sun grabbed Moon and pulled him close.

Moon wrapped his arms around him and whispered,

“Mine.”

And Sun whispered back,

“Always.”

Then they dove together.

Into the trench.

Into safety.

Into home.

But the surface wasn’t done.

Because now the humans knew two things:

1. Sirens could love.

2. And mers could love them back.

And humans?

They ruin what they don’t understand.

The surface was still above them.

The humans hadn’t given up.

The shadows of their machines cut through the reef like broken sky, like predators circling the last of their prey. They were everywhere now. The hum of engines, the lights, the artificial buzz — it never stopped. The sea was becoming a graveyard for their curiosity.

And Moon felt it. The pull of the surface — the weight of their eyes.

But he was no longer just a siren in a cage.

He was his.

And no cage would hold him now.

Sun swam beside him, quiet, steady. His tail thrummed with the steady beat of heartbeats — his and Moon’s.

They didn’t speak. No words were needed.

Sun had never asked why Moon came back for him. Never questioned his loyalty.

Moon was the first to break the silence.

“We can’t stay here, Sun.”

Sun’s eyes darkened. He didn’t need to ask. He could feel the truth in Moon’s words.

“They’ll keep coming,” Moon continued, voice low, strained. “Not just for me. For you too.”

Sun clenched his jaw. He didn’t want to hear it.

“We won’t run.”

Moon stopped. The words stung — they weren’t the same as before. The bond had shifted. Sun felt it — Moon had crossed over from just protecting him to something more primal. Something dangerous.

“We can’t stay here, Sun. Not with them watching. Not with them knowing.”

Sun turned to face him fully. “Then we fight. We make our own way.”

Moon flared his gills in frustration, voice rising in the water around them. “You don’t get it. This isn’t a fight for your reef. It’s a fight for our lives.”

And there it was. The cold truth.

The humans didn’t want them for peace. They wanted them for control. They’d pull them apart, study them, cage them in ways that would break them from the inside out.

Moon’s eyes burned. His entire form hummed with tension.

But Sun was silent, watching him closely. “And what do we do? Let them win?”

Moon stared at him, his vision swimming with bitter memories of cages, of machines, of nets — of loss.

“I won’t let them take you,” Moon hissed, sharp and raw.

Sun caught the edge of his words, stepping closer. “And I won’t let them take you.”

Moon swallowed, the weight of their shared defiance sitting heavy between them.

“We’re stronger together.”

Moon’s gills fluttered. “I know.”

Sun smiled, that bright, blinding warmth filling his chest, then glanced up at the surface. “Then we’ll show them. Together.”

The plan was dangerous. Foolhardy. Even for them.

But there was no other choice.

They gathered the reef’s bravest — those who still stood with them, who refused to bow to the surface.

The strategy was simple: bait the humans, lead them into the deep. Let them chase what they didn’t understand — the sirens and the mers together. Draw them down until the humans were lost in the trench, surrounded by the darkness of the ocean that was theirs and theirs alone.

But Moon knew one thing above all:

The reef would have to fight back.

As the humans approached, their massive vessels clunking against the coral like a storm of iron and machine, Moon took Sun’s hand. The tension between them was palpable, but neither of them looked away.

For the first time, Moon felt complete — not because of his glowing marks, his siren’s blood, but because Sun was beside him.

“Ready?” Sun asked, voice soft, lips curling into a grin.

Moon nodded. “Always.”

The humans were closer now. The lights flickered beneath them.

Moon dove first, slicing through the water like a blade. He called, his voice rising from the depths, a song so filled with power, the very water trembled around him.

It was a lure.

A deadly, sweet lullaby for those who dared to chase.

Sun followed closely behind, a flicker of light in the dark, never far from Moon’s side.

The humans followed — oblivious to the trap — until the sirens rose from the depths, a wall of darkness, their eyes glowing like burning embers.

Moon turned and faced the humans head-on. His voice cut through the water again, ringing with the force of an ancient song.

This time — there was no hesitation.

He sang not to lure.

He sang to defend.

And when the humans saw that, when they saw the fury in his eyes — the same fury that burned in Sun’s heart — they began to understand: the ocean was not something they could control.

It was something they could only respect.

But it was too late.

One of the human ships dropped its anchor — a terrible weight that cracked the surface like thunder. It pulled the others in, sinking deep.

Moon twisted in the water, singing harder, pulling the ships down into the blackness of the trench.

Sun was with him. They fought side by side, their song unbreakable.

The human machines sputtered. Lights flickered out. The reef rumbled with the surge of water, a war between the old and the new.

And in the middle of it, Sun and Moon sang.

Not to kill.

Not to maim.

But to survive.

The surface would never forget them.

And the sea would always have a place for them.

The reef was quiet.

Not peaceful — not yet.

But quiet.

After the battle, after the sirens rose from the depths and the mers stood beside them for the first time in living memory, the sea felt… changed.

Scarred, yes.

But alive.

Moon sat among the jagged coral, his arms loose around his knees, tail drifting like dark ink through the current. His markings pulsed softly with each slow breath, still dim from the strain of the fight.

Across from him, Sun hovered in the low glow of a reeflight bloom, his skin speckled with bioluminescent cuts, but his smile — somehow — hadn’t dimmed.

“You look like coral got in a fight with a stormcloud,” Sun said, leaning forward.

Moon didn’t answer.

Sun tilted his head. “Moon.”

The siren turned his head slowly. His voice was quiet, frayed. “They’ll come back.”

Sun blinked. “What?”

“The humans. They always come back. When they’re curious. When they’re afraid.”

“…And when they want something,” Sun finished, bitter.

Moon didn’t nod. He didn’t need to. The answer floated between them, heavy as salt.

“I’m not leaving,” Sun said suddenly.

Moon’s jaw tightened. “You should.”

“I won’t.”

Moon’s tail flicked, water bubbling around him in frustration. “You don’t have to stay with me. You’re not—”

“I chose you.”

Moon’s eyes finally met his.

Sun’s voice softened, but didn’t shake. “I chose you when I pulled you from the trench. I chose you when you tried to bite me. I chose you when I saw the glow in your chest and still reached for you.”

He drifted closer, fingertips brushing Moon’s wrist.

“I don’t care what you were meant to be.”

He pressed his palm to Moon’s chest.

“You’re mine. And I’m yours. Whatever happens.”

Moon stared.

For a long time, he didn’t move.

Then—his hand lifted slowly, shaking, and curled over Sun’s.

“…Even if the sea turns on us?”

Sun grinned faintly. “Then we turn the sea.”

The reef elders were silent at first.

Then… uncertain.

But they couldn’t deny what they’d seen.

A siren who bled for them.

A mer who fought with him.

Together, they’d driven back a threat no one else could face.

There were still whispers.

Still fear.

But also…

Hope.

The trench, once silent and cold, began to stir. Other sirens, curious and cautious, peered from the dark edges of their kingdom.

Some turned away.

Others watched.

And a few… drifted closer.

Moon watched them all.

But his eyes always returned to Sun.

Days passed.

Moon’s song began to return.

Not as a weapon. Not as a lure.

But as a hum in the water. Gentle. Protective.

The reef had never heard a siren sing like that.

And the reef began to sing back.

One night, beneath a curtain of soft bioluminescent anemones, Sun reached out and gently looped one of the old coral-glass trinkets back into Moon’s hair.

“You kept this?”

Moon’s voice was low, almost shy. “It was the first thing anyone gave me I didn’t have to steal.”

Sun chuckled, nudging him with his nose. “Now it’s part of the courting.”

Moon arched a brow ridge. “I thought you said that wasn’t courting.”

Sun grinned.

“I lied.”

Moon’s laugh—real, this time—rippled through the reef.

They weren’t safe yet.

The humans would return.

The ocean still trembled with change.

But for now…

Sun rested his forehead against Moon’s.

Moon closed his eyes and leaned in.

And for the first time in all his life—

Moon didn’t feel like a monster.

He felt like a mate.