I don't own D. Gray-Man or any of the legends about selkies and the like. Just so y'all know.
The witch lights aren't as bright near the settlement as they are in Sia's dark waters. He squints, knowing they dim only to hide him from the eyes of humans, who would skin him and hide the skin from him, trapping him until some hapless hunter or woodland creature freed him.
He approaches the dwelling where most of them reside: the Suspicious ones, who don't believe 'it' was just a prank; the Religious ones, who pray with fervor and beg forgiveness for imagined sins; the Children, who don't understand and might not, ever.
Sia hates them all. Even the children, who will grow with the same hate and prejudice as the adults. He wouldn't be here at all, if not for the Girl. A human who saved him. He vowed to repay her with a wish and a call, and she had called him.
He finds her at the edge of a small building, surrounded by larger humans (tall, heavily built, short hair; they are obviously male), trying with desperate eyes and heaving breath to fend them off. One look at him (slender, with silver hair in a woman's braid and glowing silver eyes, witch lights blazing behind him; otherworldly and dangerous) and they stumble away, unable to get their balance back by themselves. They flee towards the human settlement's largest house.
She smiles at him; a baring of teeth he's unfamiliar with, and is about to say something, he's sure, when two other humans turn the side of the building, ready to defend her. They pause at the sight of them: her hand in his hair, a half-formed thanks on her lips, his inhuman silver eyes and the way his pupils don't contract at the lantern they've brought, his scales and fur (oddly placed and strange to look at, after so long stuck in a human skin), the witch lights floating merrily in the background, no longer fizzing and sparking in a very real threat.
Then one of them speaks.
"Lena, what the hell?"
He curls up by the fire, only staying at the girl's insistence. His guttural moans and high-pitched shrieks served only to irritate the man who hadn't spoken, so he was silent, stretching out on the floor like an animal.
He hears the girl explain behind him, but he doesn't care enough to turn until there's a crash and a cry. He flinches into action, jumping to the girl's side and eyeing the two men in what he's heard is 'a sick look of threatening detachment'. The redhead raises his hands innocently. "What?"
He turns to the window, gaze catching on a fearful face he'd recognize anywhere, especially in the dark. It's too similar, and he swings, a whip of light and iron, and doesn't hide when the swordsman in the corner growls (no matter his instincts; he hid as a human for long enough to perfect their actions if he wished. He just doesn't want to) at the man cowering in the center of the Girl's cabin.
"Let me have this one." The swordsman grins a shark's grin, full of teeth and hate and hunger, and Sia grins right back. His teeth are longer and sharper, and he sees the Girl pale at the sight of them, so he stops, swallowing the smile and waving his hand towards the voyeur in an invitation.
"So he's repaying some debt to you?" Lavi scrapes his boot on the stones in Lenalee's walkway, rubbing off the dirt with a practiced and mindless habitual motion. Lenalee nods, blinking at the boy who twitches with animal instincts and barely repressed danger. He jumps after a butterfly in an imitation of play, getting close enough to touch but never focused enough to catch it. He returns to Lena's side before he gets too far, nuzzling into her side with a mewl. Lavi stifles the blush rising on his face.
"What's the favor you did for it?" Kanda snaps, his ire rising as the selkie fondles his childhood friend.
Lenalee smiles up at him. "Some of the villagers in a town to the west of here, many years ago, captured a pair of selkie twins and tortured them, hiding their skins and denying them water or freedom. I stumbled across the skins by accident, and when I picked them up, a voice said two names inside my head: this boy's, and the girl's. I said it, and they appeared and took their skins back. This one doesn't speak our language, but he spoke inside my head and promised me 'a wish and a call'. I guess this is my call."
The boy's mouth opened, letting loose a high-pitched wail that had them all covering their ears and kneeling in the dirt, begging him to stop.
[Hello, Girl. Men. I am called Sia, and I pledged a Wish and a Call to the Girl, yes.]
In truth, Sia wasn't sure why he tried. They simply stared at him in what appeared to be disbelief, but could just as easily have been indigestion. They didn't seem to understand at all. He sighed; typical human difficulty.
"Did you just…speak?!" The redhead ("Lavi") choked out, eyes bugging out. The swordsman ("Kanda") tightens his grip on the sharp metal stick at his side, ignoring Lenalee's sudden jolt of movement, to crouch at Sia's side and stare at him, as he follows a butterfly with his eyes. He twitches when her fingers brush his shoulder.
"Hey, you were trying to talk to us, weren't you? Sia?" He grimaces at her foul pronunciation. He hisses through his teeth, grabbing her chin and showing her, snake-like and slow. She squirms, caught between pushing him off and leaning closer, unsure what he wants, until she realizes the sound he's making imitates the name she'd said. She smiles widely. "Yes! Sia." She copies his mouth's sound, grinning when he sits back and nods, appeased. She turns to find Lavi and Kanda staring at her in open-mouthed shock, then glancing past her at the boy currently doing somersaults between the clearing's tall weeds.
"His name is Sia, is it?" Kanda finally says, the word dropping like a stone from a drowned man's mouth, hard and with a sound that echoes. Sia straightens, head jerking to face the direction of the river.
[Brother, why have you come?] He moaned, long and low, and causing the two males to grimace as their groins reacted. Lenalee just blushed.
A shadow at the edge of the clearing shifted, growing lumps and limbs where foliage and shrubbery had been mere moments ago. Witch lights flickered into life, twisting and spinning in place like firefly wind chimes.
[Why have you not yet returned? Surely the Girl has had her Wish and Call, and tires of your presence among the humans. Have you been taken yet again, Old One? You always were too beautiful for humans to let alone.] The shadow slid gracefully into the clearing. He was the mirror image of Sia, with the exception of everything (hair, eyes, the scars that littered his face and chest- he was bare. Completely naked. Lenalee flushed crimson) looking like he was spun from pure gold. A shimmering fire surrounded him and melted away, leaving a skin of the softest-looking animal skin they'd ever seen. They didn't recognize the animal, however, but Lenalee didn't need to.
"Timcampy!" She squealed, rushing forward in a happy race that led to her glomping the surprised selkie. He growled, face morphing momentarily into a nightmare creature with teeth and eyes that glowed and raved, jaws snapping inches from her neck. She didn't notice, so intent on hugging him she never saw the threat. Sia did, and casually placed his hand between her throat and Timcampy's snarling fangs.
[No, she has not yet used her Wish, dear brother. And do refrain from harming them. They're Mine.] Even Lavi could hear the capitalization in that one.
"Hey, wait a minute! What does us being 'yours' entail?" He burst out, hands on his hips. The selkies turned to stare, and he wilted beneath their apathetic gaze.
[Have you humans never heard of a Claiming?] Timcampy turned back to Sia. [They are far stupider than I had originally thought, brother.]