WARNING: The following contains spoilers for Sasuke Shinden: The Teacher's Star Pupil by Jun Esaka and Masashi Kishimoto, available in English from Viz Media now.
At the end of the Naruto series, after one last fight with Naruto that concluded with both of them losing a hand, Sasuke finally saw the light and got rid of all his hate for Konoha. He'd go on to become a Range ( still on probation mind you) as Boruto started, but because everything felt so rushed, turning him into a hero again felt a bit forced.
It was just hard to believe he could see Naruto's perspective so quickly and try to build a better shinobi world in the years that passed as a result, but in the Sasuke Shinden: The Teacher's Star Pupil novel, we discover it's not really his rival that's made him embrace the new Konoha.
Sasuke trains Boruto as a mysterious terrorist cell encroaches on Konoha's borders and tells him that science is crucial towards evolution and progress. So much so, in fact, that Sasuke, one of the most elite and naturally-gifted ninjas around, is integrating it into his career. In fact, Sasuke tells Boruto that ninja have to adapt to the current times and that change is inevitable, which is why Konoha is succeeding now. He begins speaking about how he's seen Konoha advance and this is the dream his brother, Itachi, would have loved to see become a reality.
It's not a perfect utopia but industries such as transport, science, medicine and so many others paint Konoha as a first-world land. And this innovation has spread out over the alliance as the Great Nations are all prospering. Naruto told Sasuke there'd be an era of peace, and Sasuke admits that this is what Itachi wanted. After all, it's why Itachi slaughtered his own sinister Uchiha clan. As painful as it was, Sasuke finally understands the Uchiha clan would have been detrimental to this vision, so, in essence, Naruto was executing what Itachi wanted all along: ninja living in harmony, sharing information with each other and raising kids in a time where wars have become minimal.
It's been tough to accept as Sasuke lost a lot en route to all this, but he reveals to Boruto many legends died for this to happen. In addition to Itachi providing inspiration and perishing, Jiraiya, the older Hokages such as Hashirama, Tobirama, Minato and Hiruzen Sarutobi, also left shinobi legacies and the templates for peace. This is why Sasuke enjoys science as he sees it as part of their dynasty -- after all, chakra nature and manipulation are simply tethered to energy. But most of all, this vision is what he knows Itachi would be building were he still alive. It makes sense as many fans felt Itachi should have been the first Uchiha Hokage to lead Konoha had duty not pulled him away into battle.
Boruto's surprised to hear Sasuke embracing the mistakes of old but he loves seeing and hearing how Sasuke is optimistic and hopeful in a world where child soldiers aren't needed as much. Sasuke, Itachi and Kakashi suffered due to this in their youth, so Sasuke's grateful that he can do his part in this new world -- one which is based on what his brother sacrificed his life for.
Naruto's important to the vision but it's really Itachi's words that sunk deep and got Sasuke to forgive Naruto and Konoha. And ultimately, it's why he's glad to have become part of this new, transformative era.
