Itachi and Kisame set out together on their journey to find the Bull-Headed Heavenly King.
Naruto had no intention of stopping either. He turned back toward Amegakure...
Now, he had recovered Shisui Uchiha's left eye!
I've collected both of Shisui's eyes and Kagami's right eye. To create the eternal Mangekyō Sharingan, all I'm missing is Kagami's left eye. That eye should be in Kabuto Yakushi's hands too...
Naruto's original plan had been to collect both pairs of eyes, then fuse them into the eternal Mangekyō Sharingan in one go.
But during his battle with Madara, he had learned more about the Sharingan's deeper secrets.
This was how it had happened.
Naruto said, "Madara, you have some secret dōjutsu, don't you? Something that makes Susanoo stronger!"
Madara said, "That's right. Ōfutonō-a new dōjutsu born when I awakened my eternal Mangekyō Sharingan! It doesn't need to be actively cast. It vastly amplifies the power of ninjutsu, taijutsu, and even dōjutsu!"
"I see..." Naruto had thought then, In my previous life, Sasuke's eternal Mangekyō Sharingan could eventually use Itachi's Tsukuyomi, but it never developed any new dōjutsu. As for Amenotejikara, that was an ability he acquired with the Rinnegan.
Madara said, "The transition in ocular power takes time. Sometimes, if you take too big a step, you end up overlooking things. And once you've missed them, they're gone!"
Naruto had realized with a start, Could it be... Sasuke advanced from the eternal Mangekyō Sharingan to the Rinnegan too quickly, leaving the ocular power he should have gained unawakened? Just like raising a child-some skills are hard to master as an adult if you never learned them in childhood!
Madara's words had opened Naruto's eyes and clarified how he should proceed with his own awakening!
Afterward, Naruto had taken that insight a step further.