The Bargain

todo-who:

Siren!Shinsou x Reader

Whoever is captaining this ship is a fool. Because only a fool would sail directly through siren territory at the peak of mating season.

Shinsou had, as per usual, tagged along with his sisters in their annual hunt, mainly to stave off boredom. But something feels off the closer he gets to the ship.

It isn’t until he sees you at the railing, trying to drag a man back from the brink, that he understands why. There is a roaring in his ears, his heart beating a mighty rhythm against his ribs, every instinct inside him demanding that he go to you and take you into his arms. He feels fear and anger cloud his mind when the man beside you drags you over the side of the ship and into the water. You struggle, pulling at the man with all your strength, and jealousy sears through Shinsou’s blood at the sight.

But then you manage to get your arms around the man properly and for a brief moment the two of you are side by side. Your hair and eyes are similar colors, your noses the same shape, and Shinsou realizes that the man you are desperately trying to save is not your lover but your sibling.

His sisters close in, intent on the kill, but one growl from him is enough to make them scatter.

He opens his mouth and, as the first note passes his lips, your head snaps up, eyes finding his in the murky depths. His song is one meant to soothe, a reassurance laid over a bargain. Even without words you understand, your fingers slackening around the man you’re clutching for dear life.

Shinsou swims closer, slowly, giving you ample opportunity to change your mind. But you don’t and he smiles, sharp and feral. He pushes your brother, because that’s all the man you tried to save can be, up towards the surface. It takes a moment but he seems to shake himself out of his stupor and quickly takes off, swimming for all he’s worth. You stay behind, even though your lungs must be starting to burn with the need for air.

But Shinsou won’t make you wait and darts forward, his hands cradling your face as he presses his mouth to yours, a kiss and a promise all rolled into one.

You can feel the change seep through you from that one point of contact even as you press back against him. There’s a tingling in your legs and an itch along your spine, a sharp pinch on the sides of your neck and around your ribs. You cling to the siren, gasping against his mouth with the strange sensations and sucking in a great lungful of water in the process. But instead of being painful, you blink your eyes open in surprise to find you can breathe. You can also properly see him through the gloom.

A wild mane of lavender hair floats around his face like a halo, intense purple eyes boring into your own. He is stunningly, breathtakingly beautiful and you can’t help but reach for him, awed fingers ghosting along his cheek reverently. He smiles, teeth sharp, and his hand skims down your shoulder to your bare back.

You blink and look down at yourself, realizing that your clothes have been shredded. Spiked fins jut from your elbows and wrists, wicked claws where your nails used to be. You can see blood under your arms and yank the remnants of your shirt up in a panic. But instead of bleeding wounds you find slits in your skin that part with each breath you take, the bright red of gills visible underneath. You gasp and they flare wider, but you’re quickly distracted by something else.

Where your legs used to be is instead a large tail, the scales shifting from blue to green to purple depending on how you look, the semitransparent caudal fin a dark, mottled blue. You swallow and look up, finding lavender eyes still trained on you. You open your mouth to ask his name but it comes out as a soft series of clicks, like you’ve heard dolphins make. His smile stretches wider and his response is a gentle hum you feel at the back of your neck.

“Hitoshi.” You repeat it back to him and he grins at you, reaching to lace your fingers together.

Gently, he tugs at you, leading you farther from the ship. It takes you a few minutes to get the hang of your new tail but he is ever patient, curled over your back protectively as you swim into deeper waters, away from your old life and towards your new one with him.