The demihumans themselves would be important characters. There could be a demihuman leader who Naruto teams up with.
Well, it could involve Naruto using his ninja skills to protect demihumans from various threats. Maybe they are being hunted by some evil force and Naruto steps in to save them.
They could be a fox - like demihuman, a cat - like demihuman and a bird - like demihuman. The fox - like one might have the ability to control fire, the cat - like could be super agile and the bird - like might be able to fly at high speeds. Naruto would have to use different strategies to save each of them depending on their unique characteristics.
Well, perhaps Naruto comes across the three demihumans in a dangerous situation like they are being hunted by some powerful enemy. He uses his ninja skills, like his shadow clone jutsu, to distract the enemy and then rescues the demihumans. He might then take them to a safe place in Konoha and help them adapt to the new environment.
There could be some of the older Uzushiogakure ninjas who survived the previous disasters. They would play an important role in guiding Naruto about the secrets of the village. And maybe some new characters could be introduced, like a young Uzushiogakure ninja who looks up to Naruto and helps him in his quest to save the village.
Sasuke is very likely to appear. Since he and Naruto have a deep bond, he would surely come to Naruto's aid when it comes to saving his family. Also, Sakura, as Naruto's teammate and a powerful ninja in her own right, would be there. Kakashi could also make an appearance, providing guidance and wisdom to Naruto, just like he did when Naruto was younger.
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.
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.