Alright, so this is one of those topics that gets debated to death, but I always come back to a specific scene that doesn't get enough credit: the Land of Waves arc. Everyone talks about the final valley fights, but for me, their bond was cemented the moment Sasuke took Haku's needles for Naruto. Up until then, it was just rivalry and annoyance. Sasuke was the prodigy, Naruto the dead-last. That act wasn't just about saving a comrade; it was Sasuke choosing a person over his mission-centric, revenge-driven worldview. He literally broke his own rules for someone he claimed to hate. That contradiction is everything.
Naruto's side is simpler but deeper. He saw the loneliness in Sasuke first, mirrored his own. His persistence wasn't just about being annoying; it was a refusal to let someone else stay in that isolated place. The bond developed because Naruto kept reaching out, and Sasuke, in fractured, reluctant ways, kept reaching back—like during the Chunin Exams when he tells Naruto to save Sakura, acknowledging Naruto's strength. It wasn't a smooth friendship; it was a series of fractures and desperate grabs across a widening gap, which is why it felt so real when it finally, painfully, held.