There could also be original characters created specifically for this fanfic. These new characters might have their own motives related to the Sharingan. For example, a new character could be a researcher who is trying to unlock the ultimate power of the Sharingan and sees Naruto as a key subject. They could add a whole new dynamic to the story.
In addition, characters like Kakashi, who also has a Sharingan, might have a more prominent role in this fanfic. His experience with the Sharingan could be explored in more depth, and he could serve as a mentor to Naruto in understanding and controlling the power of the Sharingan.
There could be a young and ambitious ninja as the main character in 'naruto sharingan god fanfic'. This ninja starts out as an underdog but with the discovery of the Sharingan God, their life changes completely. There might also be a mentor - like figure, perhaps an old and wise ninja who has some knowledge about the Sharingan God and helps the main character on their journey. Additionally, there could be antagonists, like other power - hungry ninjas who want the Sharingan God power for themselves.
It could be Sasuke. Since the fanfic has 'Sharingan' in the title, Sasuke, who is well - known for his Sharingan abilities in the original Naruto series, might be one of the main characters.
I'm not sure exactly as it's a fanfic, but likely there will be a character inspired by Naruto. There might also be characters related to the Sharingan's origin or those who are affected by the power of the 'holy' Sharingan.
Another possibility is that it could involve Naruto as a main character even though he doesn't have the Sharingan. His relationship with the character having the Eternal Sharingan could be explored. Maybe Naruto helps the character come to terms with their power or they team up to face a common enemy. This would add an interesting dynamic to the fanfic as Naruto's ideals and the power of the Eternal Sharingan collide and combine in different ways.
It could be Sasuke. Since he has the Sharingan, in fanfiction about the Eternal Sharingan, he might be a central figure, evolving his powers further.
Other characters like Sakura might be involved as well. She could be curious about how Naruto got the Sharingan and how it changes his abilities. Characters from the Uchiha clan, even if they are just mentioned in flashbacks, could be important. For example, Itachi's actions and the secrets he held about the Sharingan could be explored more deeply in relation to Naruto now having this power. And then there are the villains. They might see Naruto with the Sharingan as a new and greater threat or as an opportunity to gain power for themselves.
Itachi Uchiha is also extremely popular. His tragic backstory and his powerful use of the Sharingan make him a prime candidate for fanfic exploration. Writers might create stories that expand on his time in the Akatsuki or his relationship with Sasuke before his death.
Another common type of main character is a reincarnation of an ancient Sharingan user. In one fanfiction, Rei is a reincarnation of a long - dead Sharingan master. Her Sharingan has the power to see the future, and she uses this to try and prevent a great war from breaking out in the Naruto world. She teams up with Naruto and Sasuke in this story.
It could be a rogue ninja who has also obtained a corrupted form of the Rinne Sharingan. This antagonist would use the power for his own gain, causing chaos in the Naruto world. He might be seeking to overthrow all the existing shinobi villages and establish his own rule, using the unique abilities of the Rinne Sharingan like the ability to create powerful illusions that can affect entire villages at once.
It could be an evil ninja who also has a powerful form of the Sharingan. He might be jealous of Naruto's new ultimate Sharingan and wants to take it for himself. This antagonist could use his Sharingan powers to create illusions that are so powerful, even Naruto has a hard time breaking free from them.