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.
There could be a group of ancient ninja warriors who were trapped in the ruins. They might initially see Naruto as an intruder but then realize he has pure intentions and help him explore the ruins further. Another possibility is that Naruto meets the spirit of a long - dead kage. This kage's spirit could guide Naruto through the most dangerous parts of the ruins and share with him some long - lost wisdom of ruling and protecting the ninja village.
Well, Naruto might discover some powerful and long - lost jutsu in the ancient ruins. Maybe it's a super - rare form of ninjutsu that could give him an edge against his enemies.
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 the spirit of an ancient ninja.
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 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.
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 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.
He could meet some Pokemon trainers. They might come looking for the lost Pokemon egg and Naruto would have to decide whether to give it back or keep it.
He might meet Hinata. She is kind - hearted and would surely be interested in the puppy. She could offer to help Naruto take care of it, like making a little bed for the puppy.
It will likely make him more confident. With this new power, he'll be able to take on tougher challenges and succeed. This success will boost his self - esteem.