Maybe there would be a new character, a descendant of one of Raizen's old allies or enemies. This character could either help Naruto uncover more about his father or be a thorn in his side, trying to stop Naruto from reaching his full potential as the son of Raizen.
Another main character could be Kakashi. As Naruto's mentor, he would have to guide Naruto in understanding and using his powers related to being Raizen's son. He might also be the one to protect Naruto from those who would seek to harm him because of his new identity.
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.
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.
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.
Gohan himself could be a main character in some form. Maybe he exists in Naruto's memories or as a spirit guide. Another potential main character could be Sakura. She might be interested in Naruto's new powers and try to help him understand and control them. And of course, there could be new characters introduced from Gohan's world that interact with the Naruto characters.
Sasuke could be one of the main characters. He might be suspicious of Naruto's new powers and how they change Naruto. Their relationship could become more complex as Sasuke tries to understand if Naruto is still the same person he knew.
There could be Sasuke. Since Naruto's situation changes, Sasuke might play a different role in this fanfic, either as an ally or a rival in a new way. Another might be Kakashi. He could be the one guiding Naruto through his discovery of being the son of chaos.
Samul, of course, since he's Naruto's supposed father in this fanfic. He could be a powerful ninja who had some great influence in the past. Another character could be Naruto's mother, who might have a different story now considering her relationship with Samul. Also, characters like Jiraiya could still play an important role. He might be the one to guide Naruto in understanding his new identity as Samul's son and help him train to face the challenges that come with it.
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.
Iruka could be an important character. He's always been like a father figure to Naruto, and now with this new revelation, he might have to help Naruto deal with it. Hinata could also be in the story, and her feelings for Naruto could be complicated by his connection to Kisame. And then there could be some original characters created just for this fanfiction, like a ninja who was a former ally of Kisame and has some information for Naruto.
Another possibility is a group of ninja from a rival village. They fear the power that Naruto might gain from his Raizen heritage and decide to take preemptive action. They could be led by a power - hungry shinobi who believes that by eliminating Naruto, they can prevent the Hidden Leaf Village from becoming too powerful. So, they send their best assassins and warriors after Naruto.