Obviously Naruto and Kaguya are the most important. Naruto as the one to free Kaguya, and Kaguya as the one being freed.
In the 'naruto frees kaguya fanfiction', Naruto could free Kaguya through a series of events. Firstly, he might discover a hidden weakness in the seal that binds her. Then, he'd have to battle those who are protecting the seal. His Uzumaki blood and the Nine - Tails' power could play a crucial role. Once Kaguya is free, she may be grateful to Naruto and share some ancient knowledge with him, which could help in the development of the ninja world.
Obviously, Anakin is a crucial character. The slaves themselves would also be important. There could be a young slave boy or girl who Anakin befriends and who serves as a symbol of hope for the others. And the slave masters, as the antagonists, are important too.
The main characters would be Naruto and the Kyuubi. However, characters like Jiraiya could also be significant. Jiraiya, being Naruto's teacher, might have left behind some knowledge or clues that Naruto uses to figure out how to free the Kyuubi. And of course, Sasuke could be involved too. Maybe Sasuke has his own reasons for either helping or hindering Naruto's attempt to free the Kyuubi, which could add more drama to the story.
The main characters are Naruto and Kurama, of course. Naruto is the protagonist who wants to free Kurama. Kurama is the nine - tailed fox that is sealed within Naruto and is the one being freed.
Well, Naruto is the key character as he is the one who frees Jenova. Jenova herself is a central character in this fanfiction concept. Other characters from the Naruto universe could also play roles. For example, Sakura might be concerned about Naruto's actions and try to talk some sense into him. Also, there could be some original characters created for this fanfiction. Maybe a wise old hermit in the realm where Jenova was imprisoned who warns Naruto about the consequences of freeing her, but Naruto, being stubborn, doesn't listen at first.
Kakashi can be a popular character too. His wisdom and combat skills can be useful in fanfic scenarios involving Kaguya. He could be a mentor figure to Naruto, guiding him in dealing with Kaguya - related threats or helping to decipher ancient ninja knowledge related to Kaguya.
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.
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.
It's also possible that some non - human characters could be part of the harem. For example, some of the tailed beasts in human form (if that's possible in the context of the fanfiction). They would bring their own set of powers and a very different kind of relationship with Naruto compared to the human characters in the harem.
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.