Obviously Naruto would be one of the main characters. Since it's about him in some way, he'll probably be central to the story. Sasuke might also be there as he's always been an important part of Naruto's story.
Well, I think not only the well - known characters from the original Naruto series would be main characters. There could be some new characters created specifically for this fanfic. Maybe a powerful ninja from a far - away land who has some connection to Naruto's'secret strong' aspect. This new character could bring new challenges and alliances to the story.
There could be new characters introduced in this fanfiction. Maybe a mysterious ninja from a far - off land who knows about Naruto's secret and either helps or hinders him. Another possibility is that an old, forgotten character from the Naruto universe is brought back and has some connection to the secret.
Well, obviously Naruto himself would be the main character. There could also be his friends like Sasuke and Sakura, who might be involved in the interactions between the two Narutos. Maybe they are confused at first by seeing two Narutos, but then they help them figure out what's going on.
It could still be Naruto himself. Since he's the central character in the original series, many fanfics would likely continue to build on his story.
Obviously, Naruto would be one of the main characters as the story is about him being the son of Whitebeard. Whitebeard himself would also be a major character, even if he might not be around for the whole story. And then there would be the other members of the Whitebeard pirates, like Marco. They would play important roles in Naruto's life in the pirate world, either as mentors or comrades.
Obviously, Naruto and Jiraiya are the main characters. They are the focus of the 'naruto meets jiraiya' concept. Naruto, the energetic and determined ninja, and Jiraiya, the wise and powerful mentor.
Naruto is surely going to be one of the main characters. After all, it's a Naruto fanfic. Sasuke is also very likely to be there as his rival and friend. Sakura might also play an important role.
Naruto himself would probably be one of the main characters. Since he has always been about protecting his friends and the village, a 'greater good' narrative could put him in situations where he has to make even more difficult decisions regarding the well - being of everyone. He might have to sacrifice his own desires for the greater good.
Sasuke could also be a main character in the 'naruto jonin exams fanfic'. His skills and his rivalry with Naruto would make for an interesting plotline during the exams. Also, Sakura might be a main character as well. She has grown as a ninja and could show off her new abilities during the jonin exams.
From the Tsukune side, Tsukune would be there as the character being bashed. His friends from his own story might also make an appearance, but mainly to be overshadowed by the Naruto characters. For example, Moka could be in it, but the focus would be on how Naruto characters are better in various aspects compared to her and Tsukune.
Naruto himself could be a main character as the fanfic might explore how his life could have been different without the Sandaime's influence. Another likely main character could be Orochimaru, especially if the fanfic focuses on the Sandaime's failure to deal with him properly.