Chapter Text
The sea always smelled like blood when it was about to rain.
Dazai Osamu stood at the edge of the quarterdeck, boot heels pressed to the slick wood, watching the water churn like something alive. The sky bled out in bruised hues — grey, purple, and hints of red that whispered danger in the clouds. Her long black hair stuck to her face, damp from sea spray, and she didn’t bother to tie it back. The bandages on her arms had soaked through hours ago, stained from the ongoing rain.
“Storm’s rolling in,” Hirotsu said behind her.
“No shit,” she murmured, eyes locked on the horizon. She didn’t turn around. “You think we’ll find her this time?”
He didn’t answer. She didn’t expect him to.
The wind howled. The Leviathan’s Eye groaned as the waves slammed against its hull, but the crew didn’t slow. The Leviathan’s pirates never did. You couldn’t. Not when Mori was watching.
Not when you were hunting monsters.
The lookout shouted something unintelligible from the crow’s nest, and Dazai’s head tilted just slightly. She raised a hand, lazy, like a conductor calling the sea to hush.
“Say that again!” she called back.
“There’s something in the water!”
The crew scrambled to the rails, their quick movements too precise to be panic. They were trained for worse. They had seen worse. Akutagawa emerged from below deck, coat billowing from the wind and the storm-shadow magic curled inside his blade. Higuchi trailed close behind, hand on her flintlock as she scanned the horizon.
“Whales?” Kouyou asked, arms folded.
“No.” Gin had moved to Dazai’s side without a sound, eyes narrowed. “It’s singing.”
Everything stilled. Even the wind faltered, like the sea had drawn breath. Dazai’s gaze sharpened, a slow smile curling at her lips.
“Well,” she said. “We found her.”
The water was as dark and slick as oil. Beneath the surface, light pulsed — not sunlight, not lightning, but something internal. Something alive.
“Drop anchor,” Dazai commanded, “and get me a line.”
Akutagawa scowled, shedding his coat. “You’re not going in there yourself.”
“Of course not!” she said sweetly, manic glint in her eye as she slid a dagger into her belt. “You are.”
Akutagawa’s eye twitched, but he didn’t argue. He never did, not when his mentor smiled like that.
A thick rope was lowered, and the crew moved with unsettling efficiency. The Eye had done this before. They had pulled sirens and sea-wraiths from the deep, things too far gone to be called human anymore. But this one was different. This one was still fighting.
Higuchi leaned over the edge, jaw tight. “You sure it’s her?”
“No one else sings like that,” Kouyou said quietly.
And then they saw her.
The waves parted just enough to glimpse a silhouette curled in on itself, pale limbs drifting like seaweed with hair fanned out around her like fire trapped underwater. Rusted chains looped around her ankles, old magic still clinging to them like barnacles.
Akutagawa dove before anyone could stop him.
⋆⋆⋆
He returned gasping, sodden, bloodied — and not alone.
They had to hoist her up in netting threaded with salt-sigils, careful not to touch bare skin. The closer she came to the deck, the colder the air grew. Dazai watched the pouring rain transform into ice and siren frost form on the railings, the delicate fractal veins of red and black ice spreading all throughout the ship.
The siren looked fragile. Too fragile. She was small, soaked, unconscious, and wrapped in seaweed and curse-marks, her long hair tangling around her like kelp and silk.
“She’s human,” Tachihara muttered, unnerved.
“No,” Verlaine said, “she only looks it.”
Dazai stepped forward, crouched low beside the figure now sprawled in the center of the deck.
The siren didn’t stir. Her chest barely rose. There was a shimmer to her skin under the lamplight. Not glittering, but wrong, like blood diluted in water. Her lashes were long and dark, and her lips were cracked blue.
Her body was riddled with signs of tampering: scars around her throat where runes had been carved, sigils burned into her collarbones, branding from chains too old to break. Her wrists were scraped raw, and even in unconsciousness, her fingers still twitched, like they were searching for something to reach for.
“She’s perfect,” Dazai murmured.
Kouyou glanced at her. “You sound like Captain.”
Dazai’s smile didn’t change, but her visible eye darkened at the comparison to Mori. “I sound like someone who knows a weapon when she sees one.”
Akutagawa wiped sea-brine from his face and said nothing, though his hands were still hovering around his sword, ready to draw.
“What do you want to do with her?” Kaji asked, quiet. The question was for protocol, not clarity. They all knew what Mori would want.
Dazai stood. Her boots left wet prints on the deck as she walked around the siren’s still body in a slow circle.
“We don’t cage her. Not yet,” she said. “We clean her up. Bind the voice until I say otherwise. And move.”
“To Captain?” Higuchi asked.
“No.” Dazai turned. Her eye glinted. “To the wreckfields.”
“You’re detouring,” Hirotsu warned.
“I’m protecting the investment,” Dazai countered. “He sent me to find a siren. I’m not handing him over a half-dead relic before I know what she can do.”
A beat of silence.
Then Gin said, “You’re keeping her.”
It wasn’t a question.
Dazai looked down at the girl again — no, not a girl, something deeper, darker, older. The ends of her long ginger hair had begun to dry, and it tangled in strange shapes, like glyphs from some underwater god.
“Someone already tried to hollow her out,” Dazai said softly. “I’d like to see what’s left.”
Kouyou didn’t like it. Akutagawa didn’t trust it. Hirotsu said nothing, but his gaze lingered. Higuchi muttered a prayer under her breath. But none of them moved. No one ever stopped the Black Wraith, not when she spoke as if the sea had given her orders itself.
A bucket of seawater sloshed across the deck, too close to the siren’s body. Black and red scales bloomed wherever the water touched, and the sigils etched into her skin smoked. She didn’t wake, but her fingers tensed, now sharp and clawed.
“She’s reacting,” Gin observed.
“To what?” Higuchi asked.
“To the deck. The ship. Us,” Verlaine murmured.
But Dazai was kneeling again, hand hovering just above the siren’s throat. Not touching, never touching, but close enough to feel the hum beneath her skin. There was power there. Ancient and raw.
“How do we know she won’t tear us apart the second she wakes up?” Akutagawa asked.
“We don’t,” Dazai said. “That’s the fun part.”
Hirotsu muttered something about madness. Kouyou scoffed under her breath. Kaji took a silent step back. And still, the crew waited.
Chains clinked as the siren stirred. A sharp inhale. Then, slowly, the girl’s eyes opened. One was rich, ember brown — too warm, too human. The other was as blue and cold as the trench, glowing faintly in the stormlight. The air seemed to hold its breath.
Then, she screamed.
It wasn’t a scream in the normal sense. It was music, twisted and fractured — a sound that scraped along bone, that made Higuchi clutch her ears and Akutagawa stagger back, eyes wide.
Dazai didn’t flinch.
“Bind it,” she snapped.
Kouyou threw the cloth embroidered in runes with practiced speed. The gag looped around the siren’s mouth in a practiced knot. Her voice was smothered, the sound muffled beneath the cloth like thunder under skin.
She thrashed wildly, and it was clear her fangs were bared beneath the temporary muzzle. Her eyes glowed, and the magic beneath her skin spread like veins of black coral, fracturing outward.
“She’s going to crack the hull,” Hirotsu warned.
“She’ll kill us!” Kouyou hissed.
Dazai’s gaze didn’t move from the girl, who was still writhing, still caged in blood and salt. She gave a silent nod of approval and watched as they forced sedative mist through a rusted old censer, passed down from whatever beast Mori killed last. It filled the air with bitter herbs and deathroot. Slowly, the siren slumped, thrashing body now still. The frost on the rails melted, but no one paid it any mind.
Dazai stood, drawing her coat tighter. Her expression was unreadable now, except for the barest flicker in her eye. She watched the girl, the treasure they had been hunting for weeks, and smiled.
“Welcome aboard, siren.”