A/N: Warnings for (depending on what angle you approach it) hallucination induced paranoia and self-harm, and (from both sides of the fence), pill-hiding, insomnia/nightmares and suicide. I didn't think it was graphic enough for an M rating, but if anyone agrees, let me know and I'll change the rating.

Challenges:

Prompts in Steps Challenge, 5.03 - crimson

Valentines to White's Day Advent (2015), day 5 - green rose: write about a character who is sick - this sickness can be anything from minor to life-changing

Diversity Writing Challenge, g25 - fic that explores a psychiatric illness

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The Demon that Never Leaves
Chapter 1

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Duskmon wasn't there on the first night, but maybe that was because he just didn't remember it. Just a blurry moment of awakening, in which there was fear and sorrow and something wet, and then happiness and relief that washed over him like a warm blanket, and Kouji, bright but not painful to see, smiling through his tears. But the second day he was: appearing in morphine induced slumber and outside it as well, when Kouichi sat up too fast, head spinning and bile rising and thinking the nightmare was done.

It wasn't. He was there. In the corner. Watching silently as his previous host lurched forward, clutching at the blankets and fighting himself: against the acidic worm sliding up and out of his throat so he could just scream his name - except he couldn't, and he had to break that gaze otherwise he would have choked instead. And he coughed and retched and someone rubbed on his back and he twisted away until he caught the white coat - white, not black - and the distinctly human hands, and then he accepted the gesture. Because there had been only Duskmon there before. Only Duskmon and Duskmon brought no comfort: just fear and shame.

'Are you okay?' A doctor… it must be a doctor, was asking.

He was trembling now, and soaked, and the smell that drifted up to him made him shudder more but none of those could win against the need to look at that corner once more.

There was nothing there, and he couldn't quite make his throat and lips work right to ask if the doctor had seen him at all.

Stay a phantom of my mind. Please.

He wouldn't. Of course.

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They made him sleep. The doctors. The nurses. His mother. The medications. They sedated him for some sort of scan even after he promised he'd stay still for it and it wasn't fair, but apparently children never could stay still for such scans, especially if they were claustrophobic, and that made it general procedure. He wasn't claustrophobic. He wasn't afraid of the darkness either, but he fought against that sleep anyway because Duskmon was always there, hovering in his dreams, hovering when he woke up -

And nobody was there to keep him away when he slept. No sharp voices cutting through the silent assassin in the shadows. No bright lights to burn away his hiding places. No guardian to fight him off, make him leave, stuff him in a straight-jacket and a gag and a collar so he wouldn't keep on coming back like the bad memory he was.

But they couldn't. And he couldn't tell them either, not the whole truth.

As for the demon that stood in his corner.

'...sleep. It's just your head. Or the morphine. Or the fatigue. It'll all go away soon, promise.'

But Duskmon's eyes, red and boring into his very soul, promised something else entirely.

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Duskmon wasn't there when there were others in his room, right? Why not?

Except he soon realised that was wrong, when they lowered the medications and the nausea and pain eased away too. When the flurry of doctors didn't mean his entire field of vision was taken up by them. When he could see the corners and the shadows still, despite the brighter lights, despite the crowd, and see that familiar black shadow looming the back wall, watching and waiting for his chance to strike again.

Of course, they didn't know that Duskmon was a phantom that was very real. They worried about things: hallucinations that were persisting despite the other symptoms easing off. The blabbing about a demon in his nightmares, when he woke up. The way he squirmed away from touches until he could see them: their colourful clothes, their human faces.

Words were tossed around that made his mother's face go grey. Some he knew. Some he didn't. Most he didn't care about because Duskmon was a reality and not something he'd made up. The others: his brother, his friends - they could attest to that. They did, in one of those rare, hopeful moments, where he thought it really might have been just a dream. It wasn't. Remembered him. Remembered where he'd come from. What he'd done.

And of course they did. It was too much to hope for an illusion. Too easy to accept he hadn't been in the wrong except he had and it was cowardly to want a way out of the hole he'd dug himself that didn't involve him hammering in the footholds and climbing up and out himself.

Duskmon was real. And he was there, always there. It didn't matter if there was no proof of his existence. Didn't matter if, still, he escaped before his brother and his friends came because they'd recognise him for the demon he really was, and then whatever carefully laid plans involved standing there as the silent and still doorman, day and night, would be gone.

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He spoke to it, sometimes. If it could be called a conversation despite Duskmon never have anything to say in return. And why did he need to speak? Kouichi was crumbling well enough without a word from the demon.

Not when anybody else was around, though. They disbelieved and worried enough. And not for long. He couldn't stare at that demon in the corner so long. Even if he couldn't look away and draw the covers over his head and pretend there was nothing there at all.

He had to ask. 'Why..?' was the most he could often manage. 'Why are you here?' 'Why won't you leave me alone?' But no answers. Never any answers. Just more questions that rose like bile in his throat until it burned and he gulped under the covers and tried very hard not to throw up again. Sometimes he managed it. Sometimes he didn't and a nurse came running to clean things up and he'd look dully at the mess because it was all Duskmon's fault but he'd have disappeared on him by then, his task, for that point in time at least, complete.

And then there were the nightmares, where Duskmon was a more active ghost: moving, moving his body like it was a puppet and the demon pulled the strings, and the soul would just cringe away: curl in a corner and scrunch his eyes shut so he didn't have to see, and block his ears so he didn't have to hear…

But sometimes he fought past that and watched, and heard. The grinding sound of metal against the wall, just waiting until it got to human flesh. And, behind the mask, he grinned, he laughed -

Kouichi wished there was something he could use to fight back.

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The demon turned. Towards the closed door. Footsteps.

His breath caught in his throat. No. No!

It didn't matter who it was. The sword was coming up. Running along the wall again and he curled. He covered his ears. Wrenched his hands away again and his eyes open because someone was going to come through the door and they'd be dead if Duskmon got to them.

There had to be something. Something.

His breakfast, still on the tray. The cutlery. A spoon. A fork. A butter-knife. He grabbed them all and threw himself forward, towards the wall.

And screamed. Duskmon had turned to him instead, that blade punching into his palm and making him drop what he held.