Well, obviously the vixen would be a main character. Depending on the fanfiction, it could be a powerful and mysterious being with its own motives and backstory.
There might also be other characters from the Naruto series who are affected by Naruto having the vixen contract. For instance, his friends like Sasuke or Sakura. Sasuke might be jealous of Naruto's new power, or Sakura might be worried about the potential risks it brings. Also, characters like Kakashi could play a role in guiding Naruto in dealing with the powers and responsibilities that come with the vixen contract.
The dogs themselves would be very important characters. There could be a lead dog, like a wise and powerful alpha dog that Naruto forms a close connection with. Maybe Akamaru could also play a role, since he is a dog in the Naruto universe already and could be involved in some way with Naruto's new contract.
Sasuke is often a main character in such fanfictions. He could be Naruto's right - hand man, using his skills and intelligence to support Naruto's rule. Their relationship might be more complex, with Sasuke having to come to terms with Naruto's new position of power.
The demihumans themselves would be important characters. There could be a demihuman leader who Naruto teams up with.
Sakura might also play an important role. She could be one of the first to notice the changes in Naruto due to his divine connection. Maybe she tries to help him understand and control his newfound abilities, while also dealing with her own feelings for him in this new context.
There could be the princess of Altomare. She might play a crucial role in helping Naruto understand the city and its needs. Also, some of the local fishermen or sailors could be main characters as they are likely to be affected by any threats to Altomare and could assist Naruto in his guardian duties.
Well, in addition to Naruto, Gaia herself could be considered a main character in a sense, even if she might not be a physical presence all the time. If the fanfiction delves into Naruto's heritage, there could be other characters related to Gaia's past or other 'sons' or 'daughters' of Gaia in the Naruto world. And of course, Naruto's friends like Sakura would also be important. Her reaction to Naruto's new identity could range from shock to being supportive, and she might be involved in Naruto's new adventures related to his connection to Gaia.
Kakashi could play an important role. His experience and wisdom would be valuable in strategizing against the gods. Additionally, characters like Jiraiya might make an appearance, perhaps guiding Naruto from the afterlife or having left some knowledge that helps Naruto in his defiance. Another character could be Gaara. His unique abilities could be crucial in fighting against the gods' minions.
Bulbasaur - girl might be a great choice too. Her connection with nature and plant - based attacks could add an interesting dynamic. She could help Naruto understand the Pokemon world better, especially when it comes to things like finding herbs or dealing with forest - related challenges. There could also be a fiery - tempered Charmander - girl who provides a contrast to Naruto's more easy - going nature and has her own set of powerful fire - type attacks.
Well, Sasuke is likely to still be a main character. His relationship with Naruto would be even more complex if Naruto is the son of Apollo. He might be jealous of Naruto's new powers or intrigued by them. Another could be Kakashi. He would play a role in guiding Naruto in understanding and controlling his powers inherited from Apollo.
Obviously, the foxes would be the main characters. There could be an old, wise fox that acts as Naruto's mentor among them. It could have a name like Kyo, and it would be the one to teach Naruto the most important lessons.