I LOVE ME A GOOD MER-AU. LOVELOVELOVE. I've been sitting on this idea forever, (like since last may?) and finally wrote it down for you all to enjoy. (FemDeku warning b.c I'm weak)
Izumi knew she technically wasn't supposed to be doing what she was doing. It...wasn't really allowed.
Granted, she technically hadn't broken any rules either. She was staying hidden, no one had seen her, and yeah she was following a ship full of pirates around but it was fine. None of the pirates had seen her trailing after them, subtly helping where she could.
(She was attached okay. They grew on you, loud and obnoxious or not, like barnacles-)
Still- it was against the laws of her people to be seen by a human. Merfolk had disappeared into the sea for a reason, after all, and most would just as soon kill a mer than not. But...but she was curious, okay.
These men were...they were different. They were different than what mers had said humans were supposed to be. Izumi was absolutely certain of that, watching them interact with each other, and with those on the docks they stopped in.
She'd seen them interfere with Dragonborn, with Mages, with children that just needed a hand. It didn't seem to matter what sort of race those they helped had- she'd even seen a few members on the crew of the captain.
So maybe she was bending the rules a bit, maybe she sang to the oceans, urged the currents to help their ship, wove her magics into the wood, helped their ship sail through places they might not otherwise be able to sail. Maybe she sang warnings into the air, bent her magics to warn them when storms were coming, when things were going to go wrong.
Maybe she had followed them through many battles, through many events, both happy and sad, maybe she loved them all, just a bit, but she had no plans to actually reveal herself. Her entire race had been hunted to so few...the entire race had retreated to hidden coves and reefs, their magic woven so tightly around the Sanctuaries that none who were not aware and welcome inside them could enter.
Mages, and even humans with the correct instructions could create many a magical item or weave certain effects into various things ranging from clothes, to wards, to weapons, if they had the proper ingredients from a mer. Their entire bodies were saturated with magics, so much so that the magic in their scales, blood, hair, and bodies were enough to allow those who had no magic of their own to create whatever magical item or potion they were attempting.
The Huntings had caused so much pain for her people...Izumi would not cause problems by revealing herself to this crew of hers, these people she had grown to care for.
She held fast to that desire, to that belief, to the laws of her people, even months after she had started following them. Months after she had grown attached and started acting to prevent or stop rivals and enemies from touching her ship.
(Look, sure she blew up a hull or two, caused waves and choppy waters, and had once destabilized an anchor to save her humans, but it wasn't like anyone involved had seen her so it was still not breaking any laws.
She held fast when storms struck, and she watched her humans fall into the ocean, hidden from their sight, she held fast during attacks she couldn't stop, she held fast during all the events she wished she could help with.
She held herself to her silent word, until the day it became a matter of life or death.
Her secret, or the Captain's life.
The storm had been horrible, waves surging over the surface of the ocean, and sweeping onto and across the deck of the ship, lightning and wind, the sort of storm where it was near impossible to see three feet in front of your eyes on the surface.
Izumi had stuck close, following in the shadow of the ship, keeping an eye out for any troubles, and weaving strengthening magics into the wood of the boat.
And then, further up, she watched- felt- the disturbance in the waters as the Captain was knocked from the ship and into the ocean.
Her heart leapt as she watched the blonde sink, unmoving towards the sandy floor. Her eyes scanned the waves but-
But in this storm, even if his crew had seen him fall into the water, the chances of them finding him were next to nothing. The chances of the humans- or even the dragonborn- surviving the swells of the waves, the choppy, churning waters, the pelt of hard rain...keeping up with the ship, and staying strong enough to continue to do that until they were found…?
The fact that none of the Captain's crew had followed after the man was sign enough-
They hadn't seen him go over, or couldn't find him on the waves, had no idea where to start.
There's an instant, a fraction of a moment, where Izumi is frozen in the water. She was never supposed to reveal her presence. She was supposed to keep herself and her race secret. She was never supposed to be confronted with a choice like this-
Her eyes are huge as she stares.
Air bubbles escape the unmoving form, and Izumi chooses almost before she's even aware. Before she could think about it. She's moving before she knows what she's doing, choice made even before her brain catches up.
Her tail propels her through the water with a powerful swish, her billowy fins a swirl of movement. Her entire body moves with the motion, her arms and hands cutting through the waters to make an already fast movement so much quicker.
Her hands are gentle as she catches the sinking body, pulling him close to her form and directing them upwards. She breaches the water harshly, hauling the limp form up after her, using the upper part of her own tail to help brace him up while she fights the waves and wind, her magics swirling to help keep them both above the storm.
"Come on," her voice is a whisper as she works to make sure he's still breathing, no water in his lungs, or any damage from hitting the water. She can see his ship, and very distantly she can hear her crew panicking about their Captain's location over the storm.
She bites hard at her own lips, staring after the ship and closing her eyes tightly. "Aizawa-sensei is going to kill me. And mom is going to reverse the tides when she finds out about this."
She pulls a deep breath in through her nose, holding it before she shifts the pirate's form again. No choice- not if she wants this man to live. And she does.
She turns to look at the pliant form, his head- loose and obviously unconscious- cradled against her neck, nose turned towards her throat. With a soft curse, she turns, and hauls him forward, turning him to face her. It's the work of a moment to seal her lips over his own, and with a twist of her of magics, in the same moment she inhales, she can feel the ocean water rushing out of the human's lungs. She pulls backwards, and the water follows in a stream, twisting out of the man's mouth and falling back among the waves.
As soon as the last of the saltwater is gone, thanks in part to her magics, the man jolts in her hands, ruby-jewel eyes snapping open. It takes him a second to focus, and Izumi swallows her nerves as she meets his eyes.
She knows the moment he realizes what she is. His eyes flicker over her form, and then they widen, his mouth dropping just the slightest, and he whispers a soft "What the fuck?"
She doesn't hesitate to begin moving, ignoring the sting of harsh rain on her face, and how the human flails for a moment, before he seems to realize she's dragging him towards his ship, where he begins to help her by kicking his legs and generally trying to swim along with her.
Izumi feels sick, even as she powers through the water. She shouldn't have revealed herself. She really, really shouldn't have. She'd broken laws her kind had held sacred since the Hunting. She was going to be in so much trouble, but...what was she supposed to have done?
Let him die?
She could never.
She would never.
Still, her hands shake as she pulls up beside the ship, and allows the man in her arms to pull his crew's attention to himself with his voice. She even twists her magic, so the water in the air would carry it up to the crew's ears better.
Sure enough, multiple faces appear over the railing, and a ladder is lowered quickly. She holds the Captain steady in the storm surges, preventing the waves from slamming his body into the ship, or dragging him under it, as he begins to haul himself up.
She looks up at him as he climbs, pausing to look back over his shoulder, and down at her, in the waves.
She waits only until the dragonborn is reaching over the railing to haul the Captain up towards safety, before she dives beneath the waters, disappearing from their sight.
Somehow, despite the water between them, she just knew Aizawa-sensei knew what she had just done.
Bakugou Katsuki was not a man easily shocked. He'd crossed the ocean many times, had met and befriended many races that most humans lived in fear of. He had a dragonborn for a first mate, witches, mages, and elementals among his crew. He'd seen magics and acts most would call impossible or the work of a god.
He'd never seen a mermaid before.
He'd heard the tales of course. What sailor worth their sea legs hadn't? That didn't mean he had believed them.
Sirens? Those were real. He had one on his crew, and they weren't water-bound as most myths would place them. They looked human enough. But mermaids? Merfolk?
He'd never seen even a hint of those being real in his travels.
Not until he'd been knocked from his ship, voice lost in the rush of the storm, and hit the ocean certain he'd never see his crew again.
And then- then he opened his eyes, and eyes the color of the finest emeralds met his. He'd seen the scales trailing delicately over cheekbones, down her neck, and shoulders, and though her to be a dragonborn for all of two seconds, before he'd seen the jade-and-sea-and-emerald tail holding him steady before she began to swim, cutting through the storm surges and rain like they weren't present at all. He'd moved on autopilot, swimming alongside her, even as his eyes darted up and down her form, taking in the scales that trailed across her hips, up and over her chest, hiding anything from view, and down her spine and arms. He took in the curly but wet hair, the same shade of emerald forest as her eyes had been, sticking to her shoulders in the rain. He could feel how her hands shook, and fine tremors ran through her body.
He glanced over his shoulder as she easily hauled him from the water, and held his form steady against the waves as his crew threw him a ladder to climb aboard. And he saw the way she watched him, fear in her eyes, before she turned away and dove down-down-down, the only sign of her presence his survival, and the flash of flowing fins before they disappeared under the water.
He owed her his life.
He hoped that one day she would allow him to repay her.
He was a man that paid his debts.