Future Naruto could start with teaching past Naruto more efficient ways of training. For example, shortcuts to build up chakra faster. He could also introduce past Naruto to new forms of ninjutsu that he has either created or learned in the future. Moreover, he could teach past Naruto how to better communicate with the Nine - Tails on an emotional level, which could lead to a stronger bond and more powerful forms. Additionally, in terms of leadership, Future Naruto could share his experiences on leading the village, which could help past Naruto in his future leadership roles as well.
There are quite a few things. For one, he could teach past Naruto about the deeper secrets of the Uzumaki clan. Since Future Naruto has explored more about his heritage. He could also give tips on handling the Kyuubi's chakra more smoothly. Maybe some new jutsu combinations that he discovered over the years. And not to forget, how to better read an opponent's moves during a fight, which is a skill he would have refined over time.
One possibility is that future Naruto could give past Naruto some advice on how to handle his relationships better. For example, with Sasuke. He might tell him to be more understanding and patient. Also, future Naruto could show past Naruto some of his new jutsu and inspire him to train harder to reach that level.
In this fanfiction, it could also be about Naruto going back in time to learn from Kakashi. Since Kakashi was a great ninja in the past, Naruto might want to gain some skills or wisdom that he didn't have the chance to learn before. They could form a unique bond during this time, different from their relationship in Naruto's original timeline. Kakashi could be initially suspicious of this strange Naruto from the future but gradually come to trust and mentor him.
One possible plot could be that Naruto from the past somehow gets a glimpse of the future of Konoha. He sees new threats emerging and starts training in ways that can counter those threats in the future. He might also try to influence the present actions of his friends and allies based on what he saw in the future.
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.
Perhaps the plot of this 'future Naruto goes to the past fanfic' is centered around Naruto's desire to reunite with his parents. In the future, he realizes that by going back in time, he could meet them when they were alive. So, he travels to the past. Once there, he not only gets to meet his parents but also tries to change some things in the past that would lead to a better future for the entire Hidden Leaf Village. He might use his knowledge of future threats to prepare the village earlier. He could also try to influence his younger self's relationships with other characters, like Sasuke. Maybe he tries to prevent Sasuke from leaving the village in the first place by showing him a vision of the future if he does leave. This would be a very emotional and action - packed plot, full of opportunities for character development and exciting twists.
It could be a time - traveling enemy from the future who wants to stop Naruto from changing things. This antagonist might have his own motives for wanting the future to remain as it was, like having power over a ruined Konoha.
One possible plot twist could be that Naruto's love for Kakashi from the past disrupts the timeline. Maybe his feelings cause him to unknowingly change events that were supposed to happen. For example, he might prevent Kakashi from making a certain decision that was crucial in the original timeline.
In fanfiction, Hinata could teach Naruto about the Hyuga clan's gentle fist style. Since Naruto mainly focuses on his own powerful and straightforward combat techniques, Hinata's more refined and precise style could be a new area of learning for him.
He might try to change certain events. For example, he could prevent some of the tragedies that occurred in the original story. Maybe he would stop the Uchiha massacre by warning the clan or finding a way to resolve the conflict between the Uchiha and the village leadership.
In 'naruto in the future fanfiction', perhaps Naruto has passed on his ninja way to a new generation. His son or disciple could be facing a new threat that combines old and new jutsu. Maybe they have to deal with a group that has found a way to use ancient, dark jutsu in a modern, technological world.