The air left Sasuke's lungs in a painful torrent as he slammed into the ground, leaving him prone and gasping for breath. He closed his eyes against the ache flowering across his chest and silently cursed himself; he'd seen the attack, he just hadn't been fast enough to dodge it.

Someone kicked half-heartedly at the bottom of his shoe. "Is that the best you can do?" Sasuke groaned, kicking errantly at the air.

"Piss off," he ground out.

The man only prodded at him again. "C'mon, get up," he ordered. "We still have a few hours to kill." He opened his eyes to glare at Kakashi, annoyance prickling through him when he saw that the man's visible eye was crinkled in a smile.

Kakashi shrugged down at him and offered his hand. "I think that we probably exhausted taijutsu for today," he mused. "And you already reached your limit with Chidori this morning. Working on genjutsu might be a good change of pace, don't you think?"

Sasuke ignored the outstretched hand, hefting himself to his feet with a grimace. "I can keep going," he insisted.

Kakashi only raised an eyebrow in response. Sasuke waited for him to speak, a cautious hope making his blood bubble. He tried to compose his features, rolled his shoulders back in an attempt to show Kakashi that he was fine.

The disappointment was acute when Kakashi finally shook his head. "We're working on genjutsu for the rest of the afternoon."

Sasuke frowned, felt his shoulders sag. "But —"

Kakashi held up a hand. "I'm not arguing with you." He jabbed a thumb in the direction of the outpost. "We're going to head back and I'm going to teach you some genjutsu. End of story."

Sasuke cursed as Kakashi turned away from him, rubbing at the soreness in his chest now that the man wasn't looking. Kakashi nonchalantly motioned back to him.

"Language," he chided.

Sasuke rolled his eyes; Kakashi was hardly in any position to criticize him for swearing. "Whatever," he grunted, dragging his feet in a petulant show of frustration as he trailed after the man. "You hit me. Hard."

Kakashi shrugged. "We'll keep working on your speed," he placated. "You saw the attack with your Sharingan, your body just couldn't keep up."

Sasuke huffed; the irritation was burning at his skin. "I'm not improving fast enough."

Kakashi glanced over his shoulder, stopping so Sasuke could catch up. "You're improving just fine," he said once Sasuke reached him. "Your ninjutsu is already fairly advanced, and your taijutsu has improved since learning Chidori. Your genjutsu needs some work, but that's hardly unexpected since you've barely had any training in it. So try not to get so frustrated, yeah?" Sasuke flinched as Kakashi thumped the back of his head.

"Quit it," he grumbled, swatting at Kakashi and taking a step back.

Kakashi turned and continued walking, but Sasuke could still make out the smile in his voice. "Hurry up," he drawled. "I have some genjutsu tricks I think you'll like."

• • •

Sasuke would never admit it, intended to deny it with every fiber of his being if someone broached the subject with him, but, secretly, he enjoyed training with Kakashi.

It had taken Sasuke some time to warm up to the man. His indolence and nonchalance had hardly convinced Sasuke that he had anything worthwhile to teach him, and the thought of his transplanted Sharingan only made Sasuke feel as if his insides were smoldering. He'd refused to speak to Kakashi entirely at first, completely ignoring his presence for the two hours he spent at the outpost.

Kakashi, for his part, had been rather unbothered by Sasuke's attitude. He hadn't approached him, hadn't tried to cajole him into a training session — he merely sat on the couch, his feet kicked up on the table while he read a book Sasuke had never heard of.

The silence lasted for a total of eight days. Then, the thunderstorm passed.

Kakashi had glanced up at the first ominous rumble, looking fleetingly out the window before returning his gaze to his book. Sasuke hadn't thought much of his behavior, had figured that the man was only worried about having to walk home in the rain or something equally as asinine. He'd shrugged it off and stole a glance at the clock — 26 minutes before Kakashi left for the day.

Lightning lit up the room.

And then Kakashi spoke.

"Want to see something cool?" Sasuke raised a brow, turning towards the man ever so slightly. Kakashi had pocketed his book and was leaning forward, his head inclined towards the door. Sasuke only grunted, returning his attention back to the clock. 25 minutes.

He heard Kakashi shift. "Suit yourself," the man said. And then he got up and left.

Sasuke watched as the door closed behind him. He remained where he was, tried to convince himself that he wasn't at all interested in what Kakashi was doing. It was most likely something pointless, he told himself, a stupid trick he'd learned that he thought would impress the Uchiha. It was a childish tactic and Sasuke refused to fall for it. So he glared at the clock, counting down the seconds until Kakashi finally left.

He lasted exactly two minutes before he gave in and followed the man outside.

He found Kakashi in the middle of a clearing a mile or so away, his gaze trained intently on the sky above him. Sasuke scoffed at the idiocy of it all; the moron was going to get struck by lightning, he was sure of it, and he had absolutely no intention of helping him once it happened. He considered turning back to save himself the trouble, but his feet remained rooted to the ground.

Thunder growled overhead.

And then, lightning.

They'd walked back to the outpost together after in silence, Kakashi rather cheerful despite being drenched and Sasuke using the time to mull over what he'd just witnessed. He glanced at the clock as they walked inside: Kakashi had stayed for an extra 19 minutes.

Kakashi pointed towards the fridge. "Mind if I grab a drink before I leave?" He didn't wait for an answer, likely already aware that Sasuke hadn't planned on giving him one.

Sasuke, meanwhile, stood cemented at the doorway, his eyes focused on Kakashi as he made his way across the room. The lazy bastard was powerful, he'd give him that. To cut a bolt of lightning in half; Sasuke couldn't fathom the type of power someone needed to do that. The technique he had used was completely foreign to Sasuke, one he had never encountered in any scroll or book. He knew absolutely nothing about it, couldn't even begin to understand how it worked, but his chakra had thrummed when he'd seen it, the exhilaration of the jutsu making it flare.

And he knew he had to learn it.

Kakashi grabbed a bottle of water and walked back towards the door, the fridge shutting behind him. "I'll see you tomorrow, then —"

"Teach me."

It had come out quiet and stilted, less a demand and more a murmured wish. But Kakashi stopped nonetheless. He tilted his head thoughtfully. "Sorry, I didn't quite catch that. Say again?"

Sasuke grit his teeth, knew that the man was baiting him. He took a steadying breath and tried to recall the intoxicating burst of chakra he'd experienced at the mere sight of the jutsu, telling himself that this was worth it. To hold that screaming chakra in his own hand, to feel it flare through his veins; Kakashi would teach him, he had to. Sasuke just needed to ask.

And so he swallowed his pride.

"I want you to teach me."

When Kakashi didn't immediately respond, Sasuke's skin started to crawl. The man couldn't possibly deny him; he'd been sent there to teach him in the first place. But Kakashi's expression remained blank, his gaze diligently focused on Sasuke. And Sasuke couldn't help but think that reaction didn't entirely bode well for him. But he bit his tongue and waited, ever so patiently, for Kakashi to make a decision, to tell him what he was thinking.

Then Kakashi smiled, and he felt his nerves settle. "I thought you'd never ask."

And so Sasuke officially became Kakashi's student.

Kakashi refused to teach him his technique right away, had insisted Sasuke's general skillset needed to be improved upon before he could even hope to master the jutsu. Sasuke had argued, of course. He insisted that he was strong enough, that he'd been training for years and could certainly perform the jutsu if Kakashi just showed him how. So Kakashi had suggested a friendly sparring match, a chance for Sasuke to show him just how skilled he truly was. And if Kakashi was reasonably impressed, he would teach Sasuke Chidori that very afternoon.

Needless to say, Sasuke had agreed. And then subsequently got his ass kicked.

He still had yet to beat the silver haired ninja, hadn't even gotten close. But he was learning. Kakashi pinpointed every single one of Sasuke's weaknesses and spent all of his time driving at them relentlessly, forcing him to improve by sheer willpower. He extended the length of their lessons by hours at a time until he started spending most of his mornings and afternoons with Sasuke at the outpost. Sasuke hadn't complained; the more time Kakashi spent there, the more Sasuke could learn from him.

The training had gone smoothly for the first few weeks. Sasuke would end every day aching, his eyes burning from chakra strain after having his Sharingan activated for so long. But he felt stronger, felt more in control.

Or at least he had.

It happened during a fairly unremarkable training session. They had started as they normally did, facing off in the center of the clearing. Sasuke had readied himself, sinking into a defensive stance as he let the chakra collect behind his eyes. He watched intently as Kakashi lifted his headband and freed his own Sharingan, his muscles coiling in anticipation.

And then an odd twinge settled at the back of Sasuke's skull.

It hadn't felt like a genjutsu, hadn't felt like anything Sasuke had ever experienced before. He'd shrugged it off at the time, tried to focus on Kakashi and his attacks. But the pang was incessant, and it throbbed every time he looked at Kakashi's Sharingan.

He lost the sparring match. Badly. Kakashi hadn't seemed particularly perturbed by his performance, had likely chalked it up to exhaustion, but Sasuke knew it was something else. He'd felt decidedly unsteady, unfocused and unable to effectively react to any of Kakashi's attacks. And the pain in his head had only grown more distracting, biting and clawing at his brain until it had commandeered his attention entirely.

Kakashi had ended their training early that day, much to Sasuke's relief, citing a separate mission he had been assigned. He told Sasuke that he'd likely be gone for a few days, but that he fully expected Sasuke to continue training in his absence. Sasuke hadn't complained, hadn't made any smart comment; he merely nodded and reveled in the relief he felt once the man finally covered his Sharingan.

The days passed and Sasuke had begun to feel better. The pain in his head subsided, his thinking cleared, and he started to convince himself that the odd incident had just been the result of a bad day. So when Kakashi eventually returned, he'd been eager to resume training, walking straight to the clearing upon the man's arrival.

And when Kakashi unveiled his Sharingan, the twinge returned.

Sasuke didn't mention it, tried to work through the pain without bringing any attention to it. He avoided looking at Kakashi's Sharingan as best he could, staring resolutely at the man's body to try and anticipate his attacks that way. But he knew he looked distracted, could tell Kakashi was annoyed by his performance by the ferocity of his strikes. Sasuke spent more than half of the session flat on his back, bruised and bleeding and wondering what in the ever living hell was wrong with him.

"Enough," Kakashi had growled after delivering a ruthless kick to his ribs. He loomed over Sasuke, the disappointment clear on his face. A spasm of pain ran across Sasuke's temples when he spotted the red eye, making him cringe. "When you're ready to take this training seriously," Kakashi snarled, "let me know." And then Kakashi had left. And Sasuke was ashamed to admit he had been relieved.

Kakashi didn't return for awhile. Sasuke couldn't bring himself to train in his absence, could barely bring himself to get out of bed in the morning. His head was still swimming, swirling with a foggy haze that wouldn't disappear. He'd find himself staring at empty spaces for hours, losing chunks of time completely. He couldn't recall whether he was eating or sleeping, but he also didn't particularly care. All he could focus on was the merciless pounding of his brain against his skull.

Sasuke couldn't have said whether days or weeks had passed when Kakashi finally returned to the outpost. He hadn't heard the man come in, even though he had only been sitting on the couch a few steps away from the door at the time. The steady banging in his head had deafened him so completely, so totally, that he was convinced it would be the last thing he ever heard. Thump...thump...thump...

He started when the man crouched in front of him and roughly grabbed him by the chin, forcing him to look into his Sharingan.

The pain burned through him immediately, numbing his entire body and leaving him paralyzed. He wanted to beg Kakashi to let him go, to stop looking at him with that damned eye, but his tongue laid heavy in his mouth. He couldn't look away, couldn't bring himself to close his eyes even as he felt his mind slowly being torn to shreds. He thought he was going to die, truly believed that his head was going to burst at that very moment.

But then, a miracle: the thumping stopped. The haze lifted. His mind felt completely unburdened as his vision drowned in white, and he was at peace.

The agony that followed was indescribable.

Images flashed before his eyes, a cacophony of voices descending on him. He couldn't tell if he was screaming, couldn't tell if he was outwardly reacting at all to the horror unfolding in his brain. He'd been completely untethered from the physical world, thrown back into the depths of his memories. He wasn't at the outpost, Kakashi wasn't in front of him; he was at the academy learning about chakra control, with his family having dinner, swimming in the lake alongside Itachi and Shisui. There was laughter and screaming, smiles and tears, gallons upon gallons of blood, and he couldn't grab onto any of it, was unable to do anything but let it rage through him. He watched his father's neck erupt, heard his mother's screams. He saw the blur of broken, bleeding bodies as he desperately held onto Itachi, heard his own disembodied sobs. He saw white walls and a doctor, saw a man approaching him in the middle of the night with a syringe and telling him to relax, that everything was going to be fine.

The last thing he saw was Itachi crouched in front of him, his Sharingan burning brightly. He was crying.

And then Sasuke collapsed.

• • •

Sasuke wasn't sure how long he'd slept. All he knew was that he woke up at the outpost alone, his Sharingan wheeling as he flooded chakra into it. He sat up from the couch gingerly and looked at the mirror adorning the far wall. Only one thought tore through his mind.

He was going to make those fuckers pay if it was the last thing he did.