Sasuke could be involved. He might be suspicious of the artifact and think Naruto is being reckless for getting involved with it.
Maybe Naruto discovers that the weird artifact has some special powers, like the ability to open portals to other dimensions.
Maybe Kakashi. He's very experienced and wise. He could share some of his knowledge about strange things he has encountered before. He might help Naruto understand the significance of the egg and guide him on what to do with it, whether it's to keep it safe or to find its rightful place.
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.
Tsunade for sure. As the Hokage and also a medical expert, she would be furious about Naruto escaping the hospital. She might send some ninjas to bring him back.
Iruka could play a role. He was Naruto's first teacher who believed in him. He might have some small piece of information that starts Naruto on his journey to find his parents. Then there's Tsunade. As the Hokage, she has access to a lot of secret files. She could either be an obstacle, not wanting Naruto to dig too deep, or she could be a helper, providing him with crucial information. And of course, the Nine - Tailed Fox. It was sealed inside Naruto by his father, so it might have some memories or knowledge related to Naruto's parents that it could share with Naruto.
The orphans themselves would be main characters. Each one could have their own backstory and personality. Some might be shy, while others could be more outgoing. They would be the ones directly affected by Naruto's care and teachings.
There could be some original Asian - inspired characters. For example, a young martial artist from a small village in China who Naruto takes under his wing. This character could be eager to learn from Naruto and would be one of the main focuses as he grows under Naruto's guidance.
Sasuke is often involved. Since he and Naruto have a complex relationship, his reaction to Naruto's demon form can be a major plot point. He might be initially suspicious or even see it as a new way to compete with Naruto. Sakura could also be there. She might be worried about Naruto and try to find a way to help him control this new form.
Well, Sasuke could be one of the main characters involved. Since he has a complex relationship with Naruto, he might play a role in the betrayal, either as a part of the group that betrays Naruto or as someone who is conflicted about the situation. Sakura could also be involved. She has her own opinions and relationships within the Naruto universe, and she may be part of the group that turns against Naruto for some reason.
Sasuke could be involved. He and Naruto often have intertwined stories. Sasuke might either be an ally in Naruto's destruction of Iwa, or he could be there for his own reasons, like seeking power or revenge.