I think it could be count as filling this prompt (or not), tumblr / danphanwritingprompts

"What if ghosts really are all evil and have no feelings and after Danny becomes part ghost, his ghostly nature starts taking over his human one. (Basically ghosts are evil sociopaths and Danny is slowly becoming one as a result of his powers)

(Preferably with more emphasis on sociopathy being a mental disorder (ASPD), so Danny starting to be more selfish, pretty emotionless, not caring if someone gets hurt when he's fighting another ghost, etc.)"

A/N:

plays before Memories - Thursday night

I think I added it several times, maybe not (sorry, I have a poor memory), but I know it's a mess, trying to keep in track of which chapters follow the other, so for that, I recommend, my tumblr page, it has a pinned post about that: mymadmedleyw

Since Jazz knew Danny was Phantom, she couldn't say everything changed, but couldn't say it didn't.

First of all, she didn't know anything regarding ghosts or about their behaviours. During the years, growing up, she became deafer and deafer to their parents' ramblings. And eventually, it turned out as a numb background noise. She even didn't flinch to any sudden flashes, explosions or literally anything, that daily occurred in their home. But now, she wished if she would have listened. Then, maybe, now she would be capable to understand Danny more.

She couldn't say she was afraid of him, but all in all, she couldn't say either she wasn't. Not after him.

Even if Danny acted like everything was the same, Jazz could identify the resemblances, even taking the question of why she hadn't noticed until now the vicious demeanour. Maybe it was because she hadn't been paying much attention to Phantom, but then, soon, she had learned Phantom was in fact her little brother. Then she had counted the Ghost Boy as a hero and she had been worried about him. Unnoticed checking after the remains of the fights, coming up with excuses to their parents, and taking every step to protect and help him. Supporting him from the shadows, until that day.

Sure, he had hugged her, and Jazz still was giving him a hand when it had become clear she knew he was Phantom, but… since him, everything changed. It was hard to admit, but Jazz was afraid of Danny. She tried to convince herself, that her little brother wasn't changing – more like, being Phantom hadn't started to change him – but that would have been a lie. And since that, she questioned everything.

It might have been the fear, the paranoia, or the side-effects of those double electroshock that day, but her mind couldn't rest. The more she examined Danny, the more cruelty appeared. First, she tried to calculate it as tiredness, impatience and the necessary change in behaviour when he was Phantom, but Jazz just saw more of him in Danny. Even if, technically she hadn't got to know him better. But those minutes had been enough…

Acting like everything was the same was hard, especially that Danny was eluding from her since they had had that short talk about him, being Phantom. But somehow Jazz felt it was about Danny must have sensed in a way, she had begun to realise something was not okay with him.

No matter how much she was on to behave as his sister at daytime, the all came back along with that picture at night at double force when she was alone. It was hard to hide, but she had nightmares, that after two days merged with the question: what if Danny was still him? Or, worse, what if it wasn't him, but Danny would turn into him? To the one who had shocked him with those- with those red eyes, mirroring nothing but harm?

Since Jazz had learned Danny was Phantom, she perceived more from their parents' ramblings. Ghosts were nothing but a post-human consciousness, unable to feel, unable to any human emotion, just as remorse, care or anything. Jazz debated with them mentally, keeping the picture of Danny in front of her, as a reminder, telling Phantom was else, because Phantom was Danny. But what if Phantom slowly was changing her brother, to then, ten years later, became him?

Jazz couldn't escape from that theory. Not when Phantom fought with ghost cruelly, not when Danny lashed out at her, as she tried to near him, and-

What she had done? She had just let him in!

Jazz couldn't tell the cold realisation grabbed her out of the thoughts, or the suddenly felt heavy weight, landing in her face.

"Uh-" Jazz took off the object, recognising it. "Did you just throw me with a pillow?" she pointed, stunned as she put together.

"I asked you something and you weren't listening." the other explained. Jazz pushed herself up to a half-sitting position, and sent back the nice gift. But against her, he just caught it without any effort. Jazz huffed but straightaway gazed to the taller figure in the darkness, spotting as he was preparing for another one.

"Don't you dare." Jazz told him. „It's ten." she cleared, like that could mean anything to him. "If you are bored, I told you, there are options."

An unmistakable scoff was heard from the other side of the room. "I won't ever read one of your stupid books. Or fill out your even more stupid questionnaire, Jazz."

"Then occupy yourself with something." Jazz said, laying back to the bed. "I'm sure you could find out something over my options. Just let me sleep."

"You weren't sleeping." the older version of her brother called her out. "That's why I tried to communicate, but you didn't pay any attention."

"Maybe, I was sleeping." Jazz debated.

"You weren't. Don't try to convince me about the opposite."

"Fine!" Jazz rolled her eyes, instantly forgetting by this arguing where her mind had been stuck a moment ago. Because just as during daytime, she forgot everything about him, about the ghost impersonating her brother a few days ago, but right now, she just couldn't equal the two. The ghost with this current person.

"What you wanted to ask?" Jazz enquired instead, before her thoughts could return to the shrieking doubting thoughts, that what she was doing now, hiding him, a wall away from Danny, was just wrong. And a hasty stupid decision.

"Hm?" he asked after a moment as he finished with the readjusting of his made-up sleeping place, making it comfortable with that other pillow too. "Oh." he said then. "Not important." was it mumbled.

For a second, Jazz opened her mouth to push it further, because if he had thrown her with a pillow, it must have been something important, but then she gave it up instead, feeling her eyelids heavier and heavier. And much to say, it was an eventful day – or more like the afternoon needed to be rested out…

"Good night," Jazz breathed out then to the darkness. The elder version of his brother firstly just hummed, but then let out a hardly noticeable murmuring, wishing her a good sleep, so then Jazz closed her eyes.

First time, after that, now the eyes again appeared, but this time, instead of that red gaze, she was seeing the blue, identical to her little brother's as he had been looking at her during taking care of her hand. The expressions on his face were annoyed, but the bright eyes had a weird shine, that Jazz just couldn't equal with the murderous ones. In that, there had been fear, seeking for any sign of hope.

To that memory, Jazz unconsciously ran her nails on the covered injury, just to then, realising what she was doing, as she let out a hiss, scrubbing the cuts uncomfortably.

"Jazz, don't touch that." came the lecturing voice. Jazz grumbled to the tone, turning to her other side, leaving it without any note. But she couldn't cease to stare at her bandaged palm. He was so different… she couldn't tell how, but as she recalled the all afternoon, the question she had thought she missed slipped into her mind, like he would have taken it again. If you know all along, I was Phantom, why didn't you say anything?