Because
The first time he'd sacrificed everything for him, it hadn't really been only for him, it'd been more of a blanket-effecting thing, and even then he had to admit, it wasn't out of choice. But still, it had been the greatest gift the boy could give, and would haunt him for the rest his life.
The second time, the young man had thought nothing of it. To anybody else, it would have been an off-handed gesture. They would have probably found it as annoying as he pretended he did. For anybody else, it would have been an every day thing. But for he who was alone all his life, for him who hurt in the dark, blinded by misery, and rage, and solitude, just that little ebb of commiseration, that fragile thread of friendship had been more than any other had bestowed unto him, and it meant so dearly much.
The third time, he'd been his lifeline, and now they both knew he was owed his due. One had run, severing all ties, even that fragile little thread. The other had followed, dogged and persistent, he had clung to his end, faithful to his end of a one-sided bargain. He'd reached out into the black, and from it pulled the blinded child, and took him in again with not so much as a second thought. "Execute him!" had been the cry that echoed through the land of fire and leaf, but he had stood by and swore anew his oath of friendship, and thus the traitor was spared.
Why had he done these things? He'd saved him. Uzumaki, the Dead Last Ninja, the very object of his scorn.
The very boy whom the mighty and infallible Uchiha prodigy had spent his childhood belittling.
Why had he done this?
Because he wanted to prove he was better? Because he wanted the chance to laugh back, the chance for revenge? The chance to see him, with all his shell stripped away, his mask broken, and the frail, uncertain, ashamed young boy revealed?
No.
He had done it because of all the clumsy, forgetful, tactless things in the world Naruto was…
…A quitter was not one of them.
He hadn't done it to prove a point. He hadn't done it for the honor, or the fame, or the glory.
He had done it because Uzumaki Naruto and Uchiha Sasuke were friends.
He had done it…
Just because he could.
Find my place in the sun.
---------
A little bit I put out after realizing I've never written anything on Sasuke. Admittedly, he isn't one of my favorite characters, for obvious reasons. But hey, it's gotta be done sometime, right:)