"Brothers: Distance Among the Uchiha" (兄と弟 遠すぎる存在, Itachi to Sasuke Tōsugiru Sonzai) is episode 129 of the original Naruto anime.
Naruto rises from the flames unharmed, and hits Sasuke's face, but to Naruto's surprise, he acts unharmed, intimidating him. Naruto lands several blows on Sasuke's face, but even as his blood falls to the ground, he remains the same. Sasuke laughs and tells Naruto that he's not even using his Sharingan. Angered, Naruto attacks again but is blocked and pushed off of the top of the statue. Both falling off, Sasuke ruthlessly beats Naruto to the ground easily where he stays down and tosses the bag of ninja-tools to where Naruto lies. Sasuke begins to remember his childhood and his reasons for becoming obsessed with power. Sasuke's childhood was spent living in his brother, Itachi's, shadow. Being the prodigy of the clan, Itachi received all the attention from their father, leaving Sasuke to live his life trying to earn his father's recognition. Itachi, aware of Sasuke's efforts, did what he could to redirect some of their father's attention to Sasuke, but saw little success. In time, the members of the Uchiha clan began to suspect Itachi of being a murderer, and Itachi started openly attacking and disrespecting the clan.