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.
His relationship with Sasuke would be very different. If Naruto stops the Uchiha massacre, Sasuke may not have the intense hatred he had in the original story. They could grow up as friends without the need for Naruto to constantly chase after Sasuke to bring him back.
One common theme is redemption. Naruto often uses his second chance from going back in time to redeem past mistakes, especially those related to his relationship with Sakura. For example, he might correct things he said or did that hurt her in the original timeline.
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.
Well, if Naruto and Juubi go back in time, the storyline could be completely rewritten. For example, Naruto might use his knowledge of future events to prevent some of the tragedies that occurred. He could stop certain villains from rising to power earlier. And with Juubi by his side, he would have an incredibly powerful ally. This could change the power dynamics in the ninja world from the very start.
One popular plot twist could be Naruto preventing the Uchiha massacre. This would completely change the future as Sasuke's path of revenge would be derailed. It would also impact the relationship between the Uchiha and the rest of the village.
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.
I'm not sure which novel you're referring to because you didn't provide any relevant information. If you can provide more context or clarify your question, I will try my best to answer.