Boruto: Naruto next Generation Movie

Prologue

Once, there had been a war. Ootsutsuki Kaguya, who had given humans the power of chakra in the age of Myths, had been reincarnated and become an enemy to all shinobi.

The battle that took place at that time been far more intense, severe, and full of suffering than any ninja could relate in words.

In the midst of that fight, there had been two heroes. One was a man who had become a hero while Konohagakure was collapsing. Uzumaki Naruto.

The other was an aloof man who had been born into Konohagure's renowned Uchiha clan, and walked a vicissitude path because of an unfortunate turn of fate. Uchiha Sasuke.

Their fight assured victory for every shinobi. In the far off past, shinobi had descended from a single ancestor, but broken apart despite that, and fought against each other. In that victory against Kaguya, it was possible that the people called shinobi had obtained their first Union.

However, the story didn't end there.

Those shinobi's battle wasn't over. It was terribly dark...
like everything was covered in ink.

The man was running through that darkness without the slightest bit of hesitation. His eyes weren't that of an ordinary person. His eyes held a complex pattern, proof that he was person of lineage to a restricted bloodline, the holder of a doujutsu. Besides, for this man, things like the dark weren't enough to scare him.

The man's name was Uchiha Sasuke. He was a shinobi whose muscles were like a steel wire that had been forged out of the best steel, and then tempered overall. That said, it wasn't pointless sinew. His muscles were practical in the same way a leopard or lion's would be, with some faint softness of fat remaining.

So this is Ootsutsuki Kaguya's castle, huh...

In the past, Sasuke and his comrades had defeated Kaguya. It was because Kaguya had set out to have all shinobi sacrificed to her, and to absorb their chakra. It was obvious that they'd show no compassion to that sort of clan. However, it was a fact that a great mystery remained after her defeat.

Where had the Ootsutsuki come from?

What had they set out to do with the artificially made shinobi, the white zetsu?

What would be the meaning behind harvesting chakra fruit?

It boiled down to the fundamental question:

what were shinobi?

It was a shame, but the chance meeting between Naruto and Sage of Six Paths had been a once in a lifetime thing, and the information they'd gotten from the lone member of the Ootsutsuki who now lived on the moon was very little.

That was why Sasuke had spent this past ten-odd years investigating that mystery. It was because shinobi were beings who existed to gather information. Just ending a matter when its details were still unknown was unthinkable. And now, Sasuke had finally stepped foot on the historical ruins of what looked to be the Ootsutsuki Castle.

...There aren't any traces of anyone having lived here for a long time. Looks like it's best to think of it as an abandoned base.

He wondered how far they had walked. Sasuke spotted a lone scroll inside the darkness. It wasn't placed in a way that stuck out.

Amongst countless rotten scrolls, it was the only one intact. Someone without Sasuke's rare skills of observation wouldn't have been able to spot it. Sasuke carefully took the scroll into his hands, and while making sure it's outside wasn't eroded, tied it to his belt. A document that had been treated so it could withstand the passage of time had to be some confidential piece of evidence.