A/N: Pre-700? This is the first piece of fanfiction I've ever written, so please bear with any inconsistencies.
Deep down inside, Uchiha Sasuke knew he felt something for Haruno Sakura, starting from back when Team 7 was newly formed. It wasn't love. It wasn't even like. But it was something. Somewhere along the line, she had become important to him.
"Naruto, you have to save her, no matter what … I don't ever want to watch my precious people die before my eyes again."
True, for the better half of his life she had been an obnoxious follower, chasing after a boy she claimed to love but didn't even know. After they became teammates, though, her devotion became … endearing, perhaps, or at least comforting. She was one of the few people who insisted on staying by his side no matter how many times she was rebuffed, refused—the other being the dobe himself, of course. Just as Naruto had pushed and shoved his way into Sasuke's life, Sakura also took root and grew in his heart until he could hardly imagine a time without them—his entire clan gone, but those two in place of the family he lost.
But long ago, he'd slashed through whatever special place they'd carved out. It was necessary, of course, because Uchiha Sasuke was an avenger, and they were dangerous to his mission. Naruto's constant sunny smile and Sakura's never-ending sweetness allowed him to enjoy himself in a way he hadn't since the night of the massacre. They made him want to forget all about revenge and have fun instead when his true goal should have been Itachi's head on a platter.
Of course, even if he had known Itachi's secret, he should not have been cavorting around on missions for the village that had betrayed his beloved nii-san. It was unacceptable by any means. So he did what true avengers had to and cut the bonds.
"From here on out, we all begin new paths."
Leaving Sakura alone on that cold stone bench was easier than he thought it would be—Sasuke compartmentalized everything good from his genin life, shoved it into a box, and crushed it like it was nothing. Still, knowing her tears were all his fault made him sick to his stomach. He didn't have it in his heart to apologize, so he did the only thing he could—offered his sincere gratitude—and hoped she understood the underlying meaning.
Four years and a war later, when the apology finally came, he never imagined he wouldn't be welcomed back with open arms.