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Katsuki is a being of shadows. He prowls at night and looks in houses, at men and women who care too much or too little. At children who notice him more often than he likes to admit, wide eyed and staring, stricken with fear of the dark.
He often is the shadows, come to life and dancing in time with the brightness of the moon, jumping from dark place to dark place, writhing and scurrying and running from under trees to bushes, from the overcast of leaves and the push of the winds.
Katsuki is a being of shadows, and Katsuki has never seen a human who has shadows entrenched in them as deeply as this child does.
The child has mismatched eyes and hair, skin so pale in the moonlight he seems translucent, prints of blue and purple walking along the entirety of his body. Like little imprints of tiny beating hearts beneath his skin, pulsating in time with the visible discomfort and pain on his face. He reminds Katsuki of a doll, stitched up wrong and left broken, still played with despite the fraying stitches and asymmetrical make up. Used almost too much. Not taken care of enough.
The small figure is staring out of his window, body shaking from the cold, unmoving, watching the shadows dance and twirl.
Eventually a small hand stretches forwards past the windowsill, little fingers trying to touch and reach the shadows nearest him, a yearning in the stretch of his tiny limb.
So the child can see them, the shadows. The real ones, the ones that play at night.
Slowly, curious, he rises from under the tree, materializing right in front of the boy.
The kid looks up, up, until his eyes meet Katsuki's.
"Hey" he speaks, and the child jumps back and onto his floor, tiny body thumping against a tatami floor.
The kid says nothing, and Katsuki watches a shiver travel the entire length of his body.
"Don't worry" he says, unbothered by the fear. "If I wanted to hurt you, I fucking would have already".
The child only stares at him, petrified and on his back.
"Can you see the shadows? The ones that dance and play?" He asks, gruff voice echoing in the silence. Katsuki wants confirmation straight from the source.
The kid silently, shakily nods.
"How?"
But the child only shakes his head and shrugs a shoulder, hesitant, still trembling and trembling.
"You have shadows in your eyes. It's not pretty. It's the fuck ugly kind. Did you know?"
Once again the child shakes his head, and Katsuki stares, heavily, before he sits down.
"Let me guide you with them," he demands. The child shakes his head again.
"Fucking bad you don't have a choice, then" Katsuki responds, and then he pounces
***
Shouto wipes under his nose, hand covered in red and smeared on the entirety of it, pigmentation in the form of a life.
There is a laugh that resonates inside his head, full of glee, and a voice that says "Well done halfie, that was fucking beautiful".
He only hums in response as he steps over the body and leaves the alleyway, body swaying with the exhaustion of the simple act.
"Katsuki" he whispers, body seconds from giving out.
"Katsuki, I can't…"
"I know, sweetheart" Katsuki responds, something caressing his spine, the nape of his neck. Invisible lips ghosting against his throat, the side of his face.
"Don't worry, I'll take you home. You've done so good. I'll take it from here. You've done perfect".
That's all Shouto needs to hear. He finally lets go, and allows Katsuki to fully take him completely.
***
Shouto can't remember when Katsuki came into his life. To him Katsuki has always been there, a shadow that plays with him in all the ways that matter.
As a child, in pain and sad and scared after a session with his father, bruises pounding against every inch of his body.
"Poor, pathetic little baby," Katsuki would say, and run his hands through his hair, down the length of his arms. Play little games of guessing with him until his tiny body calmed down.
As a teenager, shadowy fingers running down the length of his thigh, teasing and pinching until Shouto experienced pleasure for the first time.
"See?" Katsuki had said, voice breathy. "Fucking amazing". Shouto could do nothing more than agree.
As an adult, struggling from under his father's thumb, still trying to get away. Katsuki played with him most nights, with his body, pleasure after pleasure until Shouto could not move, could not think.
All of it Shouto took and still takes happily, and in exchange Katsuki only asks for one thing.
"Be mine", and Shouto gives himself away.
Days on end where he is half aware, mind dancing in shadows as Katsuki moves his body and makes him do terrible things. Killing those who have shadow beings in them too, and then devouring said beings. He knows they don't enter him, but Katsuki inside of him.
Torturing those who have answers, from mystical creatures of the night to living people who somehow know too much.
A woman had once said "Oh child, he's taken you. You will never be free" before he plunged a knife into her stomach and gutted her, running the length of the knife across the expanse of her belly.
"Fucking amazing, goddamn perfect, Shouto" Katsuki said after that kill. Shouto found himself smiling shakily, even as the feelings of horror at the back of his head muted themselves until he could hardly tell what feelings felt like.
Katsuki makes him feel good. Katsuki makes him feel wanted, accepted, makes him feel like more then a sex toy for a man who is meant to raise him. Katsuki loves him, and Shouto will do anything for Katsuki.
According to Katsuki, the people infested with the shadow beings are not people anymore, and so it is all okay. Plus, Katsuki demands it of him, and who is Shouto to say no?
Katsuki says "jump" and Shouto lets go, and he falls.
****
He had asked, once, if they could kill his father. If Katsuki could please do it, if he would do that for Shouto.
Katsuki's answering grin, wild and feral and proud, had made him feel tingly all over. He'd crossed his legs at that look, almost involuntary, and shifted on his futon, back and forth and back and forth.
"One day" he'd answered, watching as Shouto rocked back and forth. "We have to do it, because you're mine halfie. I know you're tired of him touching you. I'm sick of it, too. Bastard taking what's mine. But not yet"
"Wh-why not?" Shouto had muttered, voice breathy and starting to rise in pitch. His hands were tucked between his legs now, too, pressing and pressing.
"Because that will be your prize, once you're ready for it. For now you gotta wait, princess."
"Okay" he'd whispered, and then he'd uttered "Katsuki, please" in a breathy tone, and Katsuki had smiled and risen above him, until Shouto was sobbing in pleasure and pain.
***
Now his father lies 6 feet under, in the backyard of the house. Shouto has killed more than he can remember, and the days pass in a blur of shadows and Katsuki and pleasure and pain.
He moans and he writhes and whines "Katsuki, please please Katsuki-" and he's left alone for so long, overstimulated as he's left tied up with a blindfold and ropes and clamps and a vibrator up his ass.
Shouto has no idea where Katsuki goes on those days, but when he comes back Katsuki loves him as he makes Shouto hurt, and his battered and thin body takes it like a balm of salvation to a weary soul.
Katsuki brings him food, and Shouto has no idea where he gets it but he eats it as Katsuki plays with him, and Katsuki is everything. He provides for Shouto and Shouto wants for nothing, even if Shouto is only allowed to go out for kills and walks around the garden, sitting within the trees and watching the shadows dance and play.
One day, as they both lay in bed, Katsuki wrapped around him instead of in him, Katsuki asks the most important question.
"Hey Shouto. Halfie. Will you let me take you?"
Shouto is confused, at first, because he has already given everything he is to Katsuki.
"I am yours. I don't. I don't understand?" He answers, his voice quiet and wispy.
"I know princess, but there is a better way. A way where we can be together forever and ever. A way for you to never, ever leave me".
"But I never will, Katsuki. I never want to leave you" he answers, fervent with the need for Katsuki to understand.
"I know sweetheart" Katsuki whispers in his ear, a bit exasperated. Shouto tenses.
"I know, but this is different. More deep. Permanent. Don't you want that too, Shouto?"
"I do" answers Shouto. Of course he does.
"Fuck yes" answers Katsuki, squeezing him. His bones ache beneath the pressure.
"Yeah" whispers Shouto, and he falls asleep under the reassurance of their eternal future.
***
The ritual happens at night. It's a night lit in silver by the full moon, the shadows around Shouto's feet dancing and twirling to the tandem of Katsuki's voice, Katsuki's shadowy figure in front of him.
His body is weak and thin, and it shivers violently under the cold of the night. But Shouto does not care, and can barely notice the purple and blue of his fingers and toes, when Katsuki is looking at him with burning red eyes.
"Ready princess?" Katsuki asks him, and Shouto nods his head sharply, awaiting their eternal union.
"That’s my Shouto, fuck" Katsuki says, and Shouto can't help the smile and the tingles that appear on his face and travel his body, pooling at the base of his belly.
"Let's begin" Katsuki demands, voice traveling, and the shadows writhe and jump and run, and Shouto watches it all with wide eyes.
As Katsuki begins, Shouto starts to feel the pain. It is a burning that begins at the base of his spine, that spreads and spreads until he is laying on the ground, shuddering and shaking and gagging, bile dribbling past his lips and onto the grass below. Katsuki never stops, even as Shouto pleads that he help him, Katsuki, please-!
Shouto never gets to see the end of it all. As Katsuki keeps chanting, Shouto stares into his shadowed face. The only thing clear in a sea of blurred visions is Katsuki's blood red, red eyes.
Katsuki grins back at him, feral and triumphant and hungry , ravenous. And Shouto can do nothing but take it as Katsuki changes his body forever, his soul, his life, as the shadows rise above him and Katsuki chants and stares at him, and his body gives up and the world around him turns to black, swallowed by the enormity of Katsuki himself.