It could also be a veteran ninja who has already seen a lot in their life but is still drawn into the Third Shinobi War. This character could have a complex backstory, perhaps they lost someone dear in a previous war and are now fighting to prevent the same from happening to others. Their wisdom and experience could be a key factor in the story.
Rock Lee could be an interesting main character for a Third Shinobi War fanfiction. Since he doesn't rely on ninjutsu, his unique fighting style could be a great asset during the war. We could see him face off against powerful ninjutsu users from other villages and prove that taijutsu is just as effective. Also, his unwavering determination could inspire his comrades during the dark times of the war.
Madara Uchiha might also be a main antagonist. His goals of reshaping the ninja world could be directly opposed to what Naruto is trying to achieve with his newfound 'godlike' powers. Madara would likely see Naruto as a major obstacle in his grand plan for the shinobi world.
It could be an original character. For example, a young ninja from a small, unassuming clan that has been overlooked in the grand scheme of the war. But as the war progresses, they show extraordinary skills and courage, becoming a key figure in the battles.
Sasuke could also be the main character. His quest for power and revenge could be further explored in the context of the war. He might find himself in situations where he has to choose between his personal goals and the greater good of his village and the shinobi world.
Naruto would be an obvious choice. He played a major role in the original 4th shinobi war. But in a fanfic, you could explore different aspects of his character, like his internal struggles during the most intense battles.
It could be an original character created specifically for the fanfic. This character could be a young ninja with a unique power or backstory, like a shinobi who has the ability to control plants in combat.
There could be some original characters as main characters too. For instance, a young shinobi from a small, unknown village who rises to prominence during the Third Shinobi War. This character could bring a fresh perspective and unique abilities to the story, interacting with the well - known Naruto characters and changing the course of the war in the fanfic.
How about a rogue ninja who has his own motives during the Fourth Shinobi World War? He might not be on either side of the main conflict, but he has a personal vendetta against one of the powerful shinobi leaders. He could be constantly interfering in the battles, causing unexpected twists and turns.
It could be an original character. For instance, a ninja from a small, unknown village who has a unique power and is forced to participate in the war. They could be the underdog that everyone underestimates at first.
In a Naruto time - travel to the Third Shinobi War fanfiction, Naruto could have a huge impact on the power balance. He could team up with younger versions of his mentors and teach them new things. For instance, he could show Kakashi some new ways to use the Sharingan that he learned from watching Kakashi in his own time. He could also influence the development of the Hidden Villages. If he helps a certain village more than he should, it could shift the political dynamics among the villages. And his presence alone could inspire young ninjas to be better and stronger, as they see someone with such unique abilities.