I do not own Homestuck. That role falls to Andrew Hussie, not that he's doing much with it at the moment. Anyways, this could be seen as JohnKat, but as it isn't specifically written as that, I'm putting it under Friendship. Enjoy!
Shooting upright in his bed, Karkat was wide-eyed and breathing hard. The nightmares were relentless, constantly reminding him of everything that had happened. This time, it was different, not just a memory. It was an idea of what could happen in the future, if his blood was ever seen by the others. The rejection, the disgust. Shuddering slightly, the troll ran a hand through his messy black hair, before he decided to get some fresh air. After creeping his way through the large house which he shared with fifteen other assholes, he stepped out of front door, wincing slightly as the cold air cut through him like a knife. The winter ground was hard and white with what the humans had called "frost" and the sky was gradually lightening as day approached. The troll settled down on the porch, closing his eyes and letting his mind empty. All of a sudden, he felt a warm hand on his shoulder. Karkat snapped his head up, quickly forcing a glare onto his face as he saw the human who stood there with a sickeningly concerned expression on his stupid derpy face. John. "What the fuck do you want?" Karkat snapped, looking back to the view.
"I was worried. I saw you go past my room and come out here, so I figured there had to be something wrong" explained John as he knelt next to the troll, the same ridiculous concern lacing his voice.
"Yeah, well you figured wrong. Everything's absolutely fucking fantastic, so you can leave me the hell alone, fuckass." was the barbed reply he got for his troubles. Realisation crossed John's face.
"Karkat...was it a nightmare again?" he asked carefully. The troll growled.
"Fuck off John." John's face lit up triumphantly.
"It was, wasn't it?" he asked, annoyingly happy about this. Did he enjoy seeing Karkat upset?
"I said fuck off!" yelled Karkat, glaring at him as he tried not to let the lingering hurt from the nightmare show. John's face softened and before the troll could react, the human's surprisingly strong arms were wrapped around him and holding him close.
"The fuck are you doing Egderp?" he shouted, flailing and trying to get away.
"Relax Karkat. It was just a dream, remember?" soothed John, ignoring the redblood's gradually lessening escape attempts and eventual submission to the embrace.
"Dumbass..." muttered Karkat quietly, but reluctantly relaxed into the other's warm hug, resting his head on John's chest and feeling peace fill his mind at the unwarranted show of affection. After a short companionable silence, John spoke.
"Karkat, if you have another nightmare, you can come and speak to me about it, okay? I'm not going to judge you, and you won't have to come out in the cold. Deal?" he asked. The troll was surprised. No-one had ever offered to do something like that for him. He was silent for a moment before finally muttering "Deal". John smiled.
"Now come inside, it's cold. You want coffee?" asked the human, releasing Karkat.
"Yeah, sure, whatever" came the reply as they both stood, causing John's face to split into that trademark derpy smile of his. "And John?" added Karkat, grabbing John's arm, turning the taller to face him. "If you ever tell anyone about this, especially Strider, I will fucking end you. Got it?" he growled angrily. John smiled again.
"Got it Karkat! Now come on, I'm freezing!" was his response, pulling the short troll towards the door and completely missing the small, but genuine smile that crossed Karkat's face.