Besides Kaguya and Naruto, Sasuke is a key character that would be involved. Their rivalry - turned - friendship makes it necessary for him to step in. Then there's Kurama, the Nine - Tailed Fox inside Naruto. Kurama might be able to resist Kaguya's control to some extent and try to communicate with Naruto's consciousness. Also, characters like Shikamaru, known for his intelligence, could be involved in devising plans to break Kaguya's control over Naruto. Other shinobi from different villages might also get involved if they realize the danger that Naruto under Kaguya's control poses to the entire ninja world.
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.
Sasuke could be involved. Since they have a complex relationship, Sasuke might either be a rival during Naruto's training, pushing him to be better, or he could end up joining Naruto in some training sessions to become stronger together.
Sasuke is likely to be involved. He and Naruto have a complex relationship and Sasuke has become an ally. He could offer his strength in combat to protect the rebuilding efforts. Also, Sakura. She's a skilled ninja with medical abilities that could be useful if there are any injuries during the process.
Sasuke is an obvious choice. He has a connection to Naruto that goes beyond just friendship or rivalry. He might be the one who first discovers Naruto's predicament and sets out to find a solution. Sakura is essential too. Her skills as a medical ninja are crucial. She could be the one who patches Naruto up every time he gets injured in his fight against whatever is threatening his life. Also, characters like Jiraiya might make an appearance. Even though he's dead in the original story, in this fanfiction, he could come back as a spirit guide to help Naruto find a way to 'refuse to die', giving him advice based on his own knowledge and experiences.
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.
Sasuke could be involved. Since he has a complex relationship with Naruto, if Naruto becomes 'Red X', Sasuke might be either an ally or an antagonist depending on the nature of 'Red X'. Another character could be Kakashi. As Naruto's mentor, he would surely notice the change and try to guide Naruto through it.
Sasuke would likely be involved. He has his own issues with Konoha and might side with Naruto, either out of friendship or his own vendetta against the village. Also, the elders of Konoha like Danzo could be important characters as they might be the ones behind Naruto's banishment.
Sasuke could be involved. He and Naruto often have intertwined stories. Sasuke might either be an ally in Naruto's destruction of Iwa, or he could be there for his own reasons, like seeking power or revenge.
All Might would probably be in it. Since he's Izuku's mentor, he could play a role in helping Izuku understand and control his time - controlling power. Maybe he has some past experience related to time powers that he shares with Izuku.
Tsunade for sure. As the Hokage and also a medical expert, she would be furious about Naruto escaping the hospital. She might send some ninjas to bring him back.
Sasuke is very likely to be involved. He has a close relationship with Naruto and is also an important figure in Boruto's life. His skills and knowledge could be crucial in any adventure or situation that Naruto and Boruto find themselves in. Another character could be Hinata. As Naruto's wife, she would surely be concerned about any strange events involving Naruto. And for Boruto, she is his mother, so she would play a role in any family - related or village - threatening situations.