I don't own Naruto but you can safely assume that this story is what would have happened at the end of the manga if I did.
Slight SasuNaru, but can be read as BrOTP IF YOU MUST.
Sasuke left in autumn.
The last view of the village behind him was orange and yellow and brown with the changing foliage and the air was crisp and clear. It felt like a good time to leave, despite Sakura's claims that a storm was coming and he should stay just a little while longer, just until it passed. He'd caught Naruto's eye across the room and his surprisingly somber expression morphed into a knowing grin. Naruto, at least, understood that it was time for him to leave.
So he'd left, more alone and unsure than he'd ever been before. But more at peace than he'd ever been before, either.
He was alone, grateful for the mild weather. Some things were still difficult, no longer second nature without the use of both hands. But he managed, kept busy enough not to really notice the quiet solitude. There were still rivers flowing and animals foraging and it was all so new that being alone was refreshing. Cleansing.
He was alone as the weather grew colder and the leaves began to fall.
They crunched beneath his feet as he walked miles and miles in a single day. He came across villages and towns but avoided them and the people in them. The solitude was comforting and the barren trees surrounding him felt more welcoming than the warm, crowded inns he passed on his way.
He no longer listened for footsteps behind him, worried that Sakura or Naruto or anyone else would stubbornly refuse to let him simply be.
(He no longer secretly wished they would appear, and he was able to stop pretending that he never did).
The quiet was nice, comfortable like clothes and sheets that smelled like home, though he had none of those things and no home.
(It took time, but eventually he stopped thinking that he had no home and started to think that maybe he still did).
He was alone in winter, sitting by a small fire as snow fell soundless around him.
He'd expected winter to be the worst, to be barren and empty and too silent. That it would remind him of all the things he knew he had to think about but was endlessly reluctant to. Or that the snow would dull his senses, freeze his mind, make him forget everything he needed to remember. He worried that the frigid blankness of winter would kill him, one way or another, and he would never have a chance to see the Sun again.
But that wasn't what winter was like.
Winter was as beautiful as a naked tree drooping with the soft snow settled on its' limbs. Winter was a surprisingly patient teacher, if Sasuke were willing to slow down enough to listen to its' advice. He walked slowly, ate slowly, made fires slowly, drifted to sleep slowly. He'd never realized before how impatient he'd been, his whole life. Winter reminded him how young he was, and how strong. Though blizzards blew and the icy wind seemed to chill him to his core, he knew confidently that he would survive.
(And more importantly, that he wanted to survive).
Everything was silent in the cold months. Even the wind seemed to blow more quietly than before. The silence and the clean air helped Sasuke's mind clear—he cleared years and years of a jumbled mess of a life in those winter months.
(It was amazing what was left inside him when everything else had been blown away).
He understood himself more with every passing day, and at night as he stared at the fire, he felt like he understood more of other people, too. There were times he almost turned back, not from loneliness—he wasn't lonely—but because he suddenly had things he wanted to share. When he looked behind him all he saw were his solitary footprints in the snow, and he turned back around and kept walking.
By the end of winter he was used to being alone, but he became suddenly lonely as the flowers began to bloom.
(The yellow ones made him think of the past, the childhood that was and the one that could have been).
For the first time in a long time he wanted a fight; something to test his skill. His missing limb no longer troubled him, but he felt that his progress had slowed.
The melting snow took him by surprise. Winter had felt so permanent, so unchanging. He had survived the cold, hard, isolated months and for the first time he wondered what Naruto was doing. How different his winter was, safe in the village surrounded by friends, learning to use his new arm… He wondered how Karin and Juugo and Suigetsu were. Wondered if Sakura still wished she'd come with him. Melting snow and ice soaked through his shoes and made noise as it dripped from trees and rocks.
(He wished winter would come back and freeze time again).
Spring was dreary and miserable and the rain made his arm ache.
It made him think about Itachi, and the fate of the Uchiha's, and his place in the story.
(He wondered, again, if they had been right to forgive him).
He wondered if he deserved forgiveness, and wondered whether living as the last lone Uchiha was a blessing or a curse. Sometimes, though he tried not to, he wondered if the world would be better off with no Uchiha's in it anymore.
Plants and animals came slowly into view. On the first really warm day, as Sasuke stopped by a quickly melting river, a bird perched itself on a branch just by Sasuke's head. Sasuke eyed it carefully, trying not to move too much. It chirped at him and he couldn't help but smile.
"Hello," he croaked, realizing very suddenly that it was the first word he'd spoken since he'd left. His voice sounded strange, gruff and deeper than he remembered. The bird hopped closer, then took off into the budding trees.
He spoke to several of the other birds he saw after that, something telling him that he needed to find ways to use his voice or he might forget how. He had things he wanted to say when he was ready to say them—and practicing on the birds was nice because they always talked back.
(Their voices were a soothing ruckas after months of calming quiet).
Yet spring only grew more miserable. It was wet and green and much too vibrant. The whole time he felt like he never got dry, and all the sights and sounds were distracting compared to his bleak, empty winter. And even with all the animals and life bursting everywhere he looked, he was still very much alone.
(He found himself thinking that being alone and being lonely were two very different things).
(He was both).
Then the warm days turned hot, he started to stay in sight of water as he walked, and the spring flowers were slowly replaced with summer grass, shooting up from the damp soil in patches everywhere he looked. The days were longer in every sense. When he woke up he was unsatisfied, spent his days brooding over what he felt was lacking, and when he stopped to sleep on damp earth he noticed a mysterious hole in his chest where he could tell something was missing but he just couldn't figure out what.
(Sometimes the missing piece of his chest bothered him more than his arm).
He was impatient and ill-tempered near the end of spring, when the rains picked back up and flooded the earth. He didn't talk back when the birds sang to him; their company wasn't enough anymore. The villages and towns he passed seemed more and more appealing, but he still never ventured near them because in his core he knew it wasn't strangers' company he wanted.
(He knew exactly whose company he wanted but stubbornly pretended that he didn't).
There was energy in the air, rippling through the leaves and branches of the trees like heat waves, but the sky remained dark and gloomy. On and on he walked in the miserable damp heat, pondering problems and solutions and right and wrong and revenge. The cloudy days depressed him and he ached all over, impatiently waiting for summer to finally break.
He started questioning what he was doing, why he was wandering across the world as if the flora and fauna would answer his many, many burning questions. He questioned his choices, angry with himself, angry with the heat and passage of time and the loneliness he'd forced upon himself. He stared up at the endless cloudy sky and felt like his journey would go on pointlessly forever.
And then, summer came. He walked slowly beneath cloudless blue skies, doubting every step. No path seemed right anymore. The way wasn't clear to him, hadn't been since the depths of his solitary winter. He no longer asked himself the important questions but spent hours asking himself why he was doing all this and which way he was going and why everything reminded him of the place he'd left all those months ago.
(The hole in his chest was bigger than ever, stretching across him and filling with his own doubts and wants and needs).
It was on a hot, blue, never-ending day of summer that Sasuke knew he couldn't do it any longer. He couldn't keep waking if this was all it was and ever would be. The loneliness was eating away at every part of him, haunting every step he took and he couldn't shake the feeling that something was missing.
And then, when the desperation had reached its peak, along the same path Sasuke was walking, baking in the afternoon sun, He appeared.
(He was as blinding as staring straight into the summer sky, with eyes just as blue).
He smiled and waved and ran to Sasuke, out of breath and panting but exuberant and enthusiastic as always. The hole in Sasuke's chest closed in the time it took Naruto to reach him.
(He couldn't recall what loneliness felt like anymore).
The sun wasn't too warm on his face anymore and the air wasn't too heavy and the ground wasn't too hard and the colors weren't too bright and the questions that plagued him flew from his head like they had wings.
(He tried not to let it show on his face).
It felt like years had passed since he'd seen Naruto's face, heard his voice. The gentle autumn and the quiet winter and the dreary, miserable spring had all left him feeling like something was missing and all it took was Naruto appearing out of nowhere, appearing despite his understanding that Sasuke had to go alone, for Sasuke to realize what had been missing the entire time.
Maybe he had needed those lonely months. Maybe he needed them to heal or to grow or to learn about himself by himself for once. But what he'd learned was that, against everything he thought he'd known about himself when he began, Sasuke Uchiha didn't like being alone.
"I know you wanted to go by yourself when you left last fall," Naruto explained. "So I didn't try to come with you then, even if I wanted to. But… it's been almost a year now and I wanted to test this new arm out and a scout spotted you around here and I figured you would have had enough of being on your own by now, right? Wasn't it lonely?"
(Yes).
"I'm not going back yet," was all he could say, before Naruto realized out how easy it would be to get him to go back.
"I know!" Naruto nodded, holding out the backpack he'd had slung around his shoulders. "I'm coming with you. However long it takes!"
Sasuke found that it was harder to keep track of the seasons when Naruto was there. Fall was never quiet with Naruto constantly blabbering in his ear and two sets of feet crunching through fallen leaves. Winter was never lonely and seldom cold with two bodies huddled around a fire watching icicles melt from the branches above them. Even dreary, miserable spring was never unbearable with birds chirping and Naruto by his side.
Summer felt like going home, because he finally had a home to go back to.
(And someone to go back home with).