The complex and nuanced relationship between Naruto and Sasuke was already defined very early in the series by one meaningful moment. During their battle against Gaara, Sasuke shows a desire to protect his friends for the first time, which in turn inspires Naruto to reach new levels of strength. However, this is also the first moment when Sasuke actually felt jealous of Naruto's power, which would later motivate him to betray Konoha and leave the village.
The relationship between the titular character and Sasuke has been a central theme of Naruto since the beginning of the series. Both kids grew up alone and orphans, but while Naruto was shunned by his fellow villagers and was generally awkward and clumsy, Sasuke was popular and recognized as a young prodigy. Naruto is jealous of Sasuke, especially of Sakura's attentions toward the Uchiha, but he also understands that Sasuke is as lonely as he is, if not more, because he actually saw his family die. That is why Naruto appoints Sasuke as his chosen rival, but their relationship quickly turns around when the Uchiha heir starts realizing Naruto's potential.
There is one moment that is a fundamental turnaround in Naruto and Sasuke's story, and it happens between chapters #133 and #134 of Masashi Kishimoto's manga. Konoha is under attack by the combined forces of Orochimaru and Sunagakure. Naruto, Sasuke, and Sakura took on the unfair task of fighting against Gaara, the host of the Ichibi. Gaara is incredibly strong and has almost defeated the trio, at which point Sasuke tells Naruto to grab Sakura and run, while he stays behind to hold off the enemy. Inspired by his friend's sacrifice, Naruto steps up, summons the chakra of Kurama inside him, and puts Gaara on the ropes by using a massive Kage Bunshin technique. Sasuke realizes that Naruto's unbelievable progress comes from a massive power hidden inside him, and begins to feel jealous of his strength.
Naruto And Sasuke's Future Relationship Was All Foreshadowed In One Sequence
The relationship between Naruto and Sasuke changes forever from this point forward. Shortly after, Naruto leaves with Jiraiya and trains to become even stronger, while Sasuke curses his own weakness. This is what motivates him to abandon Konoha and join Orochimaru, triggering Naruto's quest to save his friend, which will end only in the series finale. The battle against Gaara, however, also showed for the first time that Naruto and Sasuke make each other stronger. Naruto's pursuit of Sasuke is what motivates his growth, while Sasuke learns from Naruto that what really makes a shinobi strong is the will to protect others, not a selfish desire for revenge. This was all present, in a nutshell, in the memorable sequence in chapters #133 and #134.
The relationship between Naruto and Sasuke is perhaps the most interesting aspect of the whole Naruto series. The two characters are complementary to each other. In the end, Naruto would have never become Hokage without his pursuit of Sasuke, and, even if Naruto's growth initially spurred his betrayal of Konoha, Sasuke would have been ultimately consumed by his hatred without his friend.