It could be an ancient Hokage. Maybe one that was lost in history and had some special powers or knowledge that Naruto could use to better protect the village.
There's also a chance that it's a member of a long - extinct clan. Their unique abilities or knowledge could be of great importance to Naruto. For instance, if it was a member of a clan that could control time, Naruto could learn how to manipulate time in some way, which would be an incredibly powerful ability in his battles and his quest to bring peace to the ninja world.
It's possible that the tomb contains the remains of a powerful shinobi from the past. Naruto could learn about their history and the secrets of their power. For example, if it was an Uzumaki ancestor, he might find out more about his own clan's abilities. This could lead to him unlocking new forms of his chakra or even new ways to use the Nine - Tails' power.
In this fanfiction, Naruto might discover powerful and ancient jutsu hidden in the tomb. Maybe he'll face some dangerous traps too.
He might meet the spirit of an ancient ninja.
The buried book could be a journal from a previous Hokage. Naruto, being curious, starts reading it and discovers secrets about the village's past that help him in his future decisions. For example, it could contain details about an old enemy that is about to resurface, and the knowledge in the journal gives Naruto an edge in dealing with this threat. He might also find some words of wisdom from the past Hokage that inspire him to be a better leader for Konoha.
The Eastern Tomb of the Qing Dynasty buried five emperors of the Qing Dynasty, namely Emperor Shunzhi, Emperor Kangxi, Emperor Qianlong, Emperor Xianfeng, and Emperor Tongzhi. In addition, there were 15 empresses, 136 concubines, 3 princes, and 2 princesses, totaling 161 people.
Iruka could help. He's always been there for Naruto. He might know some old tales about mysterious eggs and give Naruto some useful tips.
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.
It could be someone who also wants the magic book. Maybe a rogue ninja who believes the power in the book can make him the most powerful in the world.
It could be an old ninja who sees Naruto's potential. This ninja might have left the sword as a way to help Naruto in his future battles.
The main antagonists could be those who want to use the Golden Army for evil purposes. Maybe some rogue ninjas who see the power of the Golden Army and plan to use it to take over the ninja world. They might try to steal the Golden Army from Naruto once they find out he has discovered it.