Because angsty ItaKaka was calling to me.
Shimmerstone
Itachi had known Kakashi since he was little. Cousin Obito died when he was five, and after that Kakashi would come around every now and then and pester some of the grown ups into helping him with the eye he'd been given. Sometimes they'd even share a lesson on it, with Kakashi trying to give examples for the theory and Itachi watching fascinated and just drinking it all in. The eye was really pretty and Kakashi was really pretty too and he was so big and awesome and a real ninja and he thought that maybe if he could get his eyes to do that then maybe they could keep on having lessons together. Later, there was an added incentive, because if he was practicing the sharingan he wouldn't have to look after baby Sasuke.
So he got the sharingan. People were awed and he felt pretty good and superior to his classmates and he got to have more lessons with Kakashi, who was doing well enough on his own, but who was taking things at a slower pace because he wasn't an Uchiha, after all, and so couldn't be expected to do as well as they did. Besides, he didn't come around so much as he used to. Kakashi was sixteen at that point, and he guessed it made sense. But he swore he'd make it so the age difference wouldn't matter.
He kept chasing the dream of Kakashi until he matched him, then surpassed him. He and Kakashi were both anbu at this point, and then Kakashi was one of his anbu, but there was still that golden edge to him, so great and so wonderful and why didn't he see him? His pretty, pretty Kakashi.
Then he realized that Sasuke didn't see him the way he saw Kakashi, because he was Sasuke's older brother, and Kakashi was… was…
He couldn't keep chasing the dream any more. It had taken him as far as he could go, but he couldn't ever have it, like a pretty, shiny river stone that wouldn't shimmer once he'd touched it.
"Don't make me your ideal, Sasuke," he said. "If you have to follow me, do it for a different reason." And he provided that reason, and gone off to follow his own path.
Maybe when he returned, Kakashi would actually look at him.
end
.: breakable dreams :.
