The sun is too bright, it hurts

The first time Sasuke sees Naruto, they are six years old. Sasuke is not stupid, he learns fast, and there are three basic things about Naruto you can know after being five seconds in the same room as him: first, he's noisy. Second, he talks a lot. Third, he's annoying.

Years later, Sasuke thinks the same, but Naruto is much more than that to him.