Naruto: Sasuke Is Reborn, Starting with Susanoo

On the night Sasuke defected, all of Konoha was stunned.

“What is this power? Could it be the legendary Susanoo?!”

Kakashi Hatake, with his single Kamui eye, was dumbfounded as he stared at young Sasuke inside the Susanoo.

He said in disbelief, “Is this what the books describe? The divine power called Susanoo, said to be awakened only by someone with two Mangekyō Sharingan?!”

“But Sasuke is only twelve! Why has he awakened the Mangekyō in both eyes?”

Tsunade and Konoha's other senior officials also stared in disbelief at the gigantic purple figure, unable to guess what Sasuke was planning.

But Sasuke did nothing. He simply grabbed Naruto and brought him inside the Susanoo, so no one could disturb them.

Then he used genjutsu to pour everything that would happen in the future into young Naruto's mind.

As Naruto clutched his head in pain, unable for the moment to believe or accept any of it,

Sasuke left him with the words, “I believe in you, my friend. Let's do our best together.” Then he took off in the Susanoo…

The future…

In the final battle, Sasuke and Naruto were ultimately killed by Isshiki. Consumed by bitter resentment, Sasuke opened his eyes once again and found himself back in the days when he was promoted to genin...

Then he began snatching forbidden techniques wherever he could find them, learning Sage Mode at Ryūchi Cave, injecting himself with the power of the Cursed Seal, filling his body with Hashirama Cells, and even fighting the Akatsuki for the Tailed Beasts.

Nagato was furious..

Everything Sasuke did was simply to collect every trump card he could use.

It was all preparation for the final battle, decades later, when the Ōtsutsuki invaded.

The synopsis can't do it justice. Please read the story itself.