In Naruto Shippuden episode 371, titled "Hole," the battle against the Ten-Tails reaches a critical point as the Allied Shinobi Forces struggle with their defense, while Naruto's power fades, leaving him vulnerable to the enemy. Concurrently, Kakashi confronts Obito in the Kamui dimension, where Obito reveals that he already knew the truth about Rin's death and argues that the Infinite Tsukuyomi is necessary to fill the emotional void in the world, while the Ten-Tails begins to transform.
You can watch the full episode and find more information on Crunchyroll and Narutopedia . Hole | Narutopedia | Fandom Naruto Shippuden Episode 371