The villains could also be important characters in this fanfic. For instance, Orochimaru or Madara might be interested in Naruto's true self, either to use it for their own evil purposes or to try and stop him from fully realizing it. Their presence would add conflict and danger to the story.
In the 'naruto heritage revealed fanfic', Naruto will surely be a central figure as the story seems to revolve around his heritage. Besides him, characters like Kakashi might be involved as he has knowledge about Naruto's father. Also, characters from the Uzumaki clan could play important roles as Naruto is from that clan. And of course, Jiraiya, Naruto's mentor, who knew a lot about Naruto's family history and the ninja world in general, might be included to help uncover more about Naruto's heritage.
In the 'Naruto Namikaze Revealed' fanfiction, Naruto is bound to be the central figure. But also, characters who are close to Naruto and would be affected by this revelation are likely to be main characters too. Sasuke, for example, as Naruto's rival and friend. His reaction to Naruto being related to Namikaze would be interesting to explore. Also, Kakashi, who was Minato's student, could play a major role. He could provide insights into the Namikaze family and help Naruto understand his new - found heritage. And then there are the village elders. Their reaction to Naruto having a stronger connection to the powerful Namikaze family would surely be a key part of the story, as it could potentially change the power dynamics within the village.
Obviously, Batman/Bruce Wayne himself is a central character. His life would be turned upside down by the revelation of his identity.
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, Batman/Bruce Wayne himself. His butler Alfred would also be heavily involved as he has always been there to support Bruce. Alfred would likely be trying to protect Bruce and keep his remaining secrets safe.
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.