Iruka - sensei might also be involved. Naruto could go to him for help in understanding the ancient book. Iruka has a good knowledge of the basics, and he could offer some initial insights or at least point Naruto in the right direction for further study.
Sasuke could be involved. He might be interested in the knowledge in the book too, and it could lead to some competition or cooperation between them. Maybe they need to work together to decipher the ancient text.
He might meet an old hermit who has been guarding the temple for centuries. The hermit could have valuable knowledge about Naruto's parents or some secret ninja arts.
He might meet an ancient sage who has been sleeping in the ruins for centuries. This sage could have a vast amount of knowledge about chakra and the ninja arts that Naruto could learn from.
He might meet the spirit of an ancient ninja.
Sasuke could be involved. He might be suspicious of the artifact and think Naruto is being reckless for getting involved with it.
Naruto might run into a group of rogue ninjas who are using the bunker as their hideout. This would lead to a confrontation where Naruto has to use his skills to defeat them and protect the village from their potential threats.
He could meet the previous Hokages. Since the library is infinite, there might be records or even some kind of spiritual manifestation of them. They could guide Naruto further in his journey.
Naruto could encounter a group of rogue ninja who are also after the treasures in the Uzumaki temple. Then he'd have to fight them off to protect the temple and its secrets.
He might meet the spirit of an ancient ninja who was the keeper of the library. This spirit could guide Naruto through the library and teach him things that no one else in the present day knows.
Her close friends would most likely be involved. Percy, for sure. He would probably be worried about her and try to sober her up. Grover might also be there, trying to use his nature - related powers to find some herbs or something that could help her feel better.
In this fanfiction, perhaps the ancient book leads Naruto on a new adventure. It could be that the book has a connection to an ancient clan, and Naruto has to uncover the truth about that clan while also dealing with the power or knowledge the book holds. For example, the book might have a map to a hidden place full of valuable resources or training opportunities. He would then have to figure out how to get there and what to do with what he finds.