Sasuke is also very popular. As Naruto's friend and rival, many fanfictions explore how their relationship would be different if Naruto had a second chance. For example, Sasuke might be more open to Naruto's friendship earlier due to Naruto's new approach influenced by his future knowledge.
One interesting plotline could be Naruto using his future knowledge to prevent certain tragedies. For example, he might stop the death of his parents. He could also use his knowledge of jutsu to quickly become a much stronger ninja at a younger age and change the power dynamics in the village.
Well, he would have a second chance at life. Since he was a baby, he could grow up with different relationships. He might form stronger bonds with his parents and be able to learn more about his family. Also, he could start training earlier and become an even more powerful ninja. With his knowledge from the future, he could also help the village in new ways, like coming up with better strategies against enemies.
Another interesting idea in this type of fanfiction is the character interactions. Naruto could interact with his parents when they were young. He could see how his father was as a young ninja, and how his mother was before she sacrificed herself. This would give him a deeper understanding of his family and his own identity. And with the Juubi's presence, these interactions could take on a whole new level of significance, as he might be able to use the Juubi's power to protect his family in the past, changing the course of his own family's history.
She could meet her younger self. This would be an interesting encounter as she could offer advice and guidance to her younger version. Maybe she could help her younger self to be less afraid of her powers.
Obviously, Naruto and Kurama are going to be main characters. Since it's about Kurama going back in time, he'll be central to the story. Naruto will also be important as Kurama's jinchuriki and the one whose life Kurama is likely to impact. Minato might also be a significant character as he was Naruto's father and had a major role in the original story. And there could be appearances from other key characters like Sasuke, as Naruto's relationship with him was a big part of the original Naruto series.
One interesting plot could be Kurama using his knowledge from the future to prevent certain tragedies in Naruto's past. For example, he might stop Orochimaru's early attacks on Konoha more effectively. Another plot could be Kurama helping Naruto train earlier and more efficiently, leading to Naruto becoming much stronger at a younger age. And perhaps Kurama could also change some of the relationships within the village, like improving Naruto's standing among the villagers much sooner.
In Juubi Naruto time travel fanfiction, plot twists can be really exciting. For instance, Naruto might find out that the Juubi has a different origin in the past than what he thought. This could completely change his perception of the tailed beasts and his role as the Jinchuriki. It could lead to him having to form new alliances or fight new enemies in the past.
Well, it could be that Naruto's strong will and his connection to all the other tailed beasts play a role. Since he has befriended the other tailed beasts, their combined energy or some sort of spiritual link might attract the power of the Juubi. For example, in some fanfic concepts, the tailed beasts' collective consciousness decides to merge their powers with Naruto, which includes the Juubi's power as the ultimate form of chakra.
One interesting plot twist could be that Naruto, with his knowledge of the future, tries to prevent certain tragedies but ends up causing new ones. For example, he might try to save a character too early and disrupt the natural flow of events, leading to unforeseen consequences.