The Hokage at the time of the banishment would be a central character. If it's Tsunade, she might have been pressured into banishing Naruto but later regrets it. Shikamaru, being one of Naruto's friends and also a strategic thinker, would probably be involved in the efforts to bring Naruto back. He could come up with plans to convince Naruto to return. Hinata, who has always had feelings for Naruto, would surely be part of the story. She might be the one to reach out to Naruto on an emotional level and persuade him to come back.
Sakura would likely be involved. She might be one of the first to realize the village made a mistake in banishing Naruto. Kakashi too, as he has always been a mentor figure to Naruto. He could be torn between his loyalty to the village and his belief in Naruto. Sasuke could also play a role. Maybe he hears about Naruto's banishment while on his own journey and decides to help bring him back when he realizes Naruto's importance to the village and to himself.
Sasuke would likely be involved. He has his own issues with Konoha and might side with Naruto, either out of friendship or his own vendetta against the village. Also, the elders of Konoha like Danzo could be important characters as they might be the ones behind Naruto's banishment.
Obviously, Naruto is the central character. But other characters like Sasuke could also be involved. Sasuke might be torn between his loyalty to Konoha and his friendship with Naruto. He could either try to bring Naruto back or join him in his exile.
The village elders are often depicted as the ones involved in Naruto's betrayal. They might see him as a threat to their power or the stability of the village. Also, some fanfictions might involve Danzo. He has always been a bit of a shadowy figure in the Naruto series, and his underhanded ways could easily be written into a plot where he is behind Naruto's false accusations and subsequent banishment.
Obviously Naruto himself would be the central character. His friends like Sasuke and Sakura would also be involved. Iruka - sensei would play an important role as Naruto's teacher at the academy again. And characters like Kakashi might also make an appearance, perhaps to give Naruto some special training or advice based on his 'second chance' at the academy.
The village elders are very likely to be involved. They often have a say in the big decisions in Konoha. They might be the ones who decide that Naruto must return for the safety or the benefit of the village. Tsunade could also be a part of it. If she's still in charge, she might be in a difficult position of having to order Naruto back or deal with the consequences of his forced return.
Definitely Naruto is the central figure. In the harem, Hinata is a very likely character since she has always been in love with Naruto. Sakura might also be there as she has been one of Naruto's closest friends. Tenten could be another addition. She has interacted with Naruto in the series and could potentially be part of the harem in this fanfiction. Also, Temari, who has had some interesting encounters with Naruto, might be a character in the harem as well.
In some fanfictions, Naruto is banished because certain powerful clans in the village see him as a threat to their power. As he is away, he might form alliances with other outcasts or powerful shinobi from other lands. When the village is in real danger, they want him back because they know only he can save them. He might return, but not without making the village face their wrongdoings first.
There could be new characters specific to the village where he becomes Kamikage. For example, some powerful shinobi clans within that village. Their leaders would be important as they could be Naruto's allies or opponents. Also, the previous Kamikage's advisors might still be around and play a role in guiding or challenging Naruto. Maybe an old sage - like figure who has deep knowledge of the village's secrets and helps Naruto understand and respect the village's heritage.
Obviously Naruto himself is the central character. Sakura might also be involved as she could be one of the few in the village who believes in Naruto's innocence and tries to help him from afar.
Obviously, Naruto himself is the central character. His friends like Sakura and Kakashi are likely to be involved too. They might support Naruto in his new adventures or face challenges alongside him.