Or, to be more precise,
this was what happened before the fight.
It was the outcome Sasuke had demanded after contacting Naruto through a special channel.
Sasuke had no objection to Naruto sending people to assist him. He wouldn't have objected even if Naruto had come himself. But that assistance had to remain external—no one else could interfere in his battle with Orochimaru. By the same token, Sasuke didn't need anyone's help to deal with Orochimaru. Sasuke was still Sasuke. Though he was far more mature than in the original story, the pride deep in his bones hadn't changed at all. He wanted to uncover the truth with his own hands, stand at the pinnacle of the Shinobi World, and revive the Uchiha Clan. For all of that, Sasuke wanted to rely on his own strength!
Naruto was his comrade.
More than that, though he wouldn't admit it aloud, Naruto was the brother he trusted most deep down!
And that was exactly why
Sasuke didn't want any unexpected factors intruding on this battle of his.
This was his fight!
The same went for his future clash with Uchiha Itachi.
If he died,
that would mean his ability and potential ended there.
Resolute and stubborn.
That was the first thought that came to Naruto's mind at the time. But Naruto had also agreed to Sasuke's request without the slightest hesitation. The reason was simple: they were both proud. A strong person needed to have their own convictions and principles.
So this desperate fight against Orochimaru
was truly a one-on-one battle between Sasuke and Orochimaru.
No one would interfere.
Orochimaru wanted to obtain the Uchiha Clan's bloodline!
Sasuke wanted to obtain all of Orochimaru's knowledge and experience.
A veritable walking treasure trove!
Whoever claimed the "fruits of victory" they wanted
would depend