In many ways, Sasuke detests Lee. Lee found a way to be a hero to everyone and not be wanted, while Sasuke was the hero everyone wanted but refused to be. He hates Lee because nothing came easy to him but he was still grossly optimistic, and Sasuke hates optimists. He hates Lee because Lee loved Sakura and let her reject him time and time again in Sasuke's name.
Sasuke once told Lee every reason he hates him. Lee only smiled and said hate was an unnecessary emotion. Sasuke nearly punched him and told him hate was necessary to accomplish anything because without it the task cannot be appreciated. Lee only dodged and told Sasuke he was wrong.
A week later Sasuke returns to Konoha with a mangled corpse slung over his shoulder and a pair of spinning Mangekyou eyes sending Sasuke's vision from black to white and back again every few seconds. Itachi Uchiha is buried with the rest of the Uchihas a few days later. Lee asks Sasuke if he feels anything. Sasuke says nothing. Lee says Sasuke couldn't need Hate to kill his brother, considering he obtained the Mangekyou. Sasuke smiles and kisses Lee's cheek.
Three days later Sasuke is missing.
Four days later Naruto's body is found.
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Yes, Sasuke's crazy 8D He wouldn't smile otherwise >