Episode 107 is widely considered the beginning of the arc. It is a "canon" episode, meaning it follows the original manga's storyline directly and is essential viewing for understanding the characters' motivations before the jump to Naruto Shippuden .
The episode highlights Sasuke's descent into darkness as he realizes his "sword to protect bonds" (Chidori) was unable to scratch Itachi, while Naruto's power is rapidly surpassing his own. Naruto Episode 107
Just as the two are about to clash, Sakura runs between them to stop the fight. Kakashi arrives at the last second to redirect their attacks into water tanks, revealing the devastating difference in power between their respective jutsus. Why This Episode Matters Episode 107 is widely considered the beginning of the arc