Both in the anime and manga, Sasuke decided to leave Konoha and he went to
Orochimaruís side to gain power. He wanted to defeat Itachi so badly, that
he finally went to Orochimaru because Orochimaru promised him power.
Tsunade then dispatched a team of chuunin and genins that includes Naruto, Shikamaru, Chouji, Kiba, and Neji to retrieve Sasuke.
The team that was sent to retrieve Sasuke and was severely injured, and even Chouji died when he fought with Jiroubo.
When Naruto was fighting Kimimaro in the forest, the barrel that had Sasuke in it exploded and revealed Sasuke which was possessed with Orochimaruís 2nd level curse.
Sasuke ran to the fire countryís border when Naruto called him, and soon after, Naruto ran after him, leaving Rock Lee, who just came to battle with Kimimaro.
After Naruto caught up with Sasuke, Sasuke still refused to go back. So Naruto decided to drag him back by fighting Sasuke. Sasuke obliged, and he fought Naruto back.
It was a sad battle, Naruto was trying hard to make Sasuke see that the path that Sasuke chosen was the wrong path. He talked to Sasuke about their memories as team seven, and about Naruto seeing Sasuke as his friend, rival . . . and brother.
Sasuke said that he sees Naruto as his brother too, but if he wants to beat Itachi, he have to take this path.
Naruto, enraged, changed into Kyuubi, and Sasuke changed into Orochimaruís second form curse. Sasuke now looked like a demon . . . with wings.
Naruto charged at Sasuke with Rasengan, and Sasuke charged Naruto with chidori. The battle ended with Sasuke standing over Narutoís unconscious form, and that Sasuke couldnít kill Naruto even though he has to kill him if he wants to obtain the Magenkyo Sharingan. But Sasuke left Naruto alive, to be picked up by Kakashi later.
Team seven . . . was breaking.
Submitted by tezuka_zone