Obviously, the reincarnation of Kaguya would be a main character. Naruto or Sasuke could also be main characters as they might be involved in the discovery of the reincarnation and have to decide whether to trust her or not.
Kaguya herself could be a main character in a sense. Through flashbacks and the influence she has on her reincarnation, she could drive the plot. Additionally, characters from the Otsutsuki clan might be main characters as they might be interested in the reincarnation of Kaguya for their own purposes, either to use her power or to prevent her from becoming a threat.
Obviously Naruto would be one of the main characters since it's about him being the heir of Kaguya. Sasuke could also be a main character as Naruto's rival and friend. Sakura might be involved too, as she is part of Naruto's team. And there could be other characters like Kakashi, who would play a role in guiding Naruto as he discovers his new identity. There might also be some new characters introduced that are related to Kaguya's past, who either help or hinder Naruto on his journey.
Sasuke would most likely be involved. Since he has a strong bond with Naruto, he would sense something is wrong and try to free Naruto from Kaguya's control. Sakura might also be part of it as she cares about Naruto and would be determined to save him. Kakashi could play a role too, using his wisdom and experience to figure out a way to break Kaguya's hold on Naruto.
Well, in fanfiction, the idea of Naruto being Kaguya's reincarnation might be a really interesting concept. It could potentially bring in new storylines and character developments. Some fanfiction writers might do this to explore different power dynamics or to create a new connection between the characters. But it's important to note that this is not part of the official Naruto lore.
It could be a rogue ninja who wants to use the descendant for their own power - gain. Maybe someone who believes that by controlling the descendant, they can access Kaguya's ultimate power. For example, a power - hungry ninja who has been researching Kaguya's secrets for a long time.
Sasuke can also be involved in some cases. Since he and Naruto are often together in many situations, Sasuke's presence might add some complexity to the relationship between Kaguya and Naruto. For example, Sasuke might be suspicious of Kaguya's intentions towards Naruto at first.
The two main characters would be Naruto and Kaguya for sure. However, depending on the plot, other important characters from the Naruto universe could make an appearance. It could be the tailed beasts, as Naruto has a strong connection with them. If the situation involves something related to the chakra of the ninja world, the tailed beasts might be involved in some way. Or perhaps characters from the Otsutsuki clan could be relevant if Kaguya's actions are related to her clan's history or powers.
Obviously Naruto would be one of the main characters. Since it's about his reincarnation related to Sparda. But there might also be characters from the Naruto series like Sasuke, Kakashi etc. who would be involved in the story. And depending on how the Sparda aspect is incorporated, there could be some new characters related to Sparda's world as well.
Obviously, Naruto would be one of the main characters as he is the one who is the reincarnation of Kisuke. And Kisuke himself, even if only in the context of his past life or the influence he has on Naruto. There might also be other Naruto - related characters like Sasuke, Sakura, etc., as they would interact with Naruto in this new situation of his reincarnation.
Naruto is surely one of the main characters since it's about his reincarnation. And there would likely be his friends like Sasuke and Sakura. Also, characters related to the Sage of Six Paths might play important roles, either as allies or antagonists.
Besides Obito, Sasuke could be a main character in this fanfiction. Sasuke, with his own journey of redemption and his understanding of power and the ninja world, could have an interesting dynamic with the reincarnated Obito. Also, Sakura might play a role. She could be the one who tries to heal the reincarnated Obito, both physically if he is injured during his new adventures and emotionally from the traumas of his past life.