Obviously, Naruto himself is the most affected as he has to deal with the knowledge of the future. But his friends like Sasuke, Sakura, and Kakashi would also be deeply affected. If Naruto saw a future where Sasuke was in trouble, he would do everything to change it, which would impact Sasuke's life. Sakura, being Naruto's teammate and also caring about Sasuke, would be involved in any plan Naruto made. And Kakashi, as their sensei, would be there to guide and support them through the changes Naruto tries to make based on his future vision.
The villains in the story could also be affected. If Naruto saw a future where a particular villain was about to cause a great catastrophe, he could take preemptive action. For example, if Orochimaru was planning something big in the future that Naruto saw, Naruto could try to stop him earlier than in the original storyline. This would change the dynamics of Orochimaru's character arc and how he interacts with other characters.
Obviously, Naruto would be the main character since it's about his past seeing the future. Sasuke would also be important as Naruto's relationship with him is central to the Naruto series. Kakashi too, as he is Naruto's teacher and mentor, and his guidance might be influenced by Naruto's new - found knowledge of the future.
It could be a new character, perhaps someone from a far - off land who has a grudge against Naruto's future self for some reason. This character might be extremely powerful and has plans to destroy everything Naruto holds dear. When Naruto sees this future, he has to find a way to stop this new threat before it even begins to form.
The main characters are Naruto and his comrades. Iruka, Naruto's first teacher, could be in it too. He has always been like a father figure to Naruto. In the fanfiction, he might be one of the first to notice something strange about Naruto's future. Then there are Naruto's other friends from the village like Kiba and Choji. They would all react differently to seeing Naruto's future. Kiba might be more impulsive in his actions to change it, while Choji might be more cautious but still determined to help Naruto have a better future.
Naruto's children would likely be main characters. They would inherit his strength and determination. Also, the students of the new generation of ninja academies could play important roles as they strive to make their mark in a world shaped by Naruto and his peers.
Naruto is the central character, no doubt. Hinata could be important as well. If Naruto sees a future related to his family or his relationship with Hinata, she will play a significant role. Additionally, the Hokage, like Tsunade or whoever is in charge at that time, would be important as Naruto may need to report the future he saw to the village leadership to take collective action.
Well, in this fanfiction, Naruto might see himself as Hokage finally achieving all his dreams. He could see his friends and family thriving in a peaceful Konoha. Maybe he'd also see new generations of ninja being trained under his guidance.
Well, one possibility could be that Naruto has some sort of visionary ability where he can see snippets of the future during his past adventures. For example, he might see the final battle against Kaguya while he's still on a mission with his team as a genin. This could change his approach to training and how he interacts with his friends, as he tries to prepare them for what's to come.
Maybe new characters could be introduced as main characters in this fanfiction. For example, a young shinobi from a small village who stumbles upon the future orb and becomes the key to understanding its power. Or an old hermit who has some hidden knowledge about the orb and guides the more well - known Naruto characters in their journey with it.
One possible plot twist could be that Naruto sees a future where his friends turn against him. This would shatter his world as he values his friendships deeply. He might then struggle to figure out what went wrong in the future and try to prevent it in the present.
Obviously Naruto himself is the most important as he's the one seeing the future. Sasuke would likely be there too, as he's Naruto's closest friend and rival. Sakura would probably also play a role, maybe as a skilled medical ninja in the future Naruto sees. Kakashi might also show up, perhaps as an elder guiding Naruto in his leadership role.