Sometimes he couldn't help but look towards home, no matter where he was.
When his nightmares showed him the face of his brother betrayedwhywhywhywhy he would often use his Sharingan to show himself better memories and tried to shove down the guilt. He had plenty of good memories, even if all of his time in those last few months had been eaten by ANBU, even if he'd made and broken so many promises of helping him practice or train.
He knew that going through with it was a mistake, but at the time he honestly couldn't see another way, no matter how much he put his supposedly genius mind to the task. It hadn't been until the deed was done and he'd reported straight to the Hokage instead of Danzo that he'd realized just what happened. He'd been able to use that to ensure his brother's future safety at least.
He would sometimes disappear for days at a time, the only reason he wasn't questioned too much was because he would bring back good intel or a nice bounty (or two... or ten... or twenty), they didn't need to know that he returned to watch over Konoha, often imagining what his brother was doing and hoping that he was becoming strong.
Once in a while he would be joined by an old monkey, and they would just sit in silence. Sometimes the monkey would leave with a scroll in hand, sometimes not.
He'd often watch, from the distance, a bright haired and brightly clothed child leading various adults on merry chases; he'd spent an hour once watching that child graffiti the Hokage Monument, laughing when he realized that nobody noticed. He laughed more watching the ensuing chase when the child finally announced his presence. The next time the monkey came to see him, he made sure to mention it along with the scroll. The next time he returned, the monkey made a vague comment that a mass training schedule had been devised for every Ninja that had been in the village that day.
He knew who the child was, of course. His raven had returned to Rain one day and shared the news that his brother was now on a team with that bright haired child, his old captain, and a pink haired girl who's name he only recognized from a merchant family.
Memories had assaulted him of protecting that child, of watching over him as he slept, of playing with him, of making sure he enjoyed his birthday for once, of bringing his brother to play with him. Unfortunately, the good relationship his brother and that child used to have seemed to have disappeared. He'd hoped that his brother might be able to find some happiness, but it seemed he'd latched onto the limited teachings their father had passed on of their clans' superiority.
The next time the monkey visited him, he left with a Summons scroll, a tanto, a letter to his old captain, and an old scroll he'd once taken from the clan library and never had a chance to return before that night.
He listened to the orders stoically. Capture the Nine-tailed Fox container.
He managed to delay their arrival in the village until after his raven came back with the news that the boy wasn't in the village any longer. He'd left in the presence of the Toad Sage the night before. He neglected to mention this to his partner, however. He sighed when he realized how easy it was to slip into the village, they were supposed to be on high alert right now, the Hokage had just been killed and their village invaded. How was it this easy to get in?
He almost choked on his tea when he realized his brother was right there, and so was his old captain. He knew the moment the old hound realized who he was, and knew that it was going to be much more difficult to get out then it had been to get in. Oh well, they'd been here long enough, and heard enough for his partner to realize for himself that their target wasn't here. He almost sighed when his captain subtly alerted the Hokage's son to their presence as well and requested back-up. His captain did not, however, make any indication of just who he was... curious. At least he managed to plant a scroll on his old captain before using the Genjutsu on him.
The next time he sat on his ledge overlooking the village, it was a small pug dog that left with a scroll safely tucked into his collar.
The encounter when they finally found their target went as he'd expected hoped it would go, with the unexpected addition of his brother showing up.
He sighed. His brother hadn't grown stronger, just hate-fueled. While he had told the boy to hate him, he'd hoped that the counselors would have steered him in another direction. He had seen them, hadn't he? Or had the stupid council stuck their long, unwanted noses into things that were none of their concern? Unfortunately he hadn't been able to keep a very close eye on his brother in the months following that night, he'd been too busy establishing himself within the organization, and then later almost killing himself a snake. He still regretted letting that monster slip through his fingers, especially after the Sannin succeeded in poisoning him.
Maybe he would go snake hunting after this, he had some frustrations to work through...
So far he'd been unable to find a cure. Not even a covert visit to the Slug Princess had yielded many results. He'd only been able to slow it's fatal effects, hoping that he'd be able to last long enough to see this through.
Unfortunately, he knew that any hope of him ever coming back to the village had died along with the Third Hokage, unless he'd left a message somewhere for his predecessor.
(If his partner hadn't been there, watching, he never would have used that Genjutsu on his brother. His captain was well trained and strong, he could handle it. He worried about what this would do to his brother's already revenge-fueled mind.)
Some time later, the small pug was joined by a slug. He almost sighed in relief when she'd helped alleviate his growing symptoms and discomfort. Unfortunately a cure wasn't any closer to being found. That snake was devious, he would give him that.
Oh well, by now he'd made peace with his lot. As a Ninja, he'd always known that he could die at any time, it was something he'd accepted early in his life. Frankly he was amazed to have made it this long considering everything.
The urge to go snake hunting got stronger the more he heard about the fight that his brother's age group went through to get him back when he defected, lured to the snake's side with the promise of power. While he knew that he wasn't strong healthy enough to hunt the snake (and he still had things to do), he made sure to make his presence known in the area around the snake's main hide-out for a while. He wasn't surprised when the snake packed up and moved headquarters within a week. He just followed them, and made sure to stay nearby either his village or the snake when he wasn't in Rain.
He was growing weaker. His partner had started noticing. It was hard to hide it when he stumbled the other day. Again, the slug helped, but they both knew he was running out of time. He'd finally admitted to his partner that he was sick, had been for years. Since then, his partner made sure he rested as much as possible, ate well, and started doing the majority of the work on their missions. To his knowledge, his partner never said a word to Leader.
He counted himself lucky to have a good relationship with his work partner. They could be like the Immortal pair, constantly arguing and trying to kill each other.
When the bright-haired target left the village with the Toad Sage, he started keeping an ear out and detouring to see him whenever they were in the same area. If the Toad Sage questioned the jutsu scrolls and intel that made their way into his pack, he never gave any indication of it. He was pleased to see the boy working out of one of the scrolls he provided the next time he saw them.
If his partner noticed anything about his actions (it was harder to keep things from him when he was paying such close attention, afraid his health would take a downturn at any moment), he never said anything.
When he received word that the Snake was dead, he knew it was almost time. Time for him to test his brother's strength one last time, he only had one good fight left in him.
He extracted a promise from his partner to watch out for his brother, paid a final visit to the ledge overlooking the village (the pug left with a scroll and the slug grimly alleviated his symptoms once more), and went to where he knew his brother would find him, an old, nearly forgotten Uchiha stronghold near the border of Fire.
Facing his brother, he was proud of how strong he'd become, and knew that he could finally rest. His job here was done, it was time for the next generation to take charge.