Well, he could change the course of history. Maybe he'd prevent some of the tragedies that happened in the original Naruto story. For example, he might stop the Uchiha massacre by warning the clan or influencing Itachi in some way.
He could also use his knowledge from the future to help train his younger self or his friends more effectively. He might introduce new jutsus earlier or teach them different strategies. This could make them all much stronger much sooner in the story. He could also have an impact on the relationships between different characters. For instance, he could encourage Naruto to be more open with Sakura about his feelings, or vice versa.
Another possibility is that Naruto entering the past could disrupt the balance of power in the ninja world. His presence and his future knowledge could attract the attention of powerful enemies or allies. He might have to deal with people who are either trying to use him for their own gain or trying to stop him from changing the past. And this could lead to a whole new set of adventures and challenges for Naruto.
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.
Well, she might discover Naruto's hidden fears. Naruto often puts on a brave face, but inside he could be scared of losing his friends. Ino, with her mind - entering ability, could stumble upon these deep - seated fears and try to comfort him in his mind - scape.
Well, in a fanfiction where Naruto travels to the past, he could meet his parents when they were young. He could also learn new jutsu from the past ninjas that were lost over time. Maybe he'd even be able to influence the early development of the Hidden Leaf Village in ways that would make it stronger in his own 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.
Naruto could also meet the previous Hokages in their prime. He could learn from them directly and perhaps even influence their decisions. For example, he might be able to convince the First Hokage to handle the Uchiha clan's situation differently, which could have a huge impact on the future (or in this case, the future that Naruto comes from).
In such a fanfiction scenario, Naruto might use his knowledge from the future to prevent some disasters. For example, he could stop the Uchiha massacre by warning the clan early. He could also teach his younger self some advanced jutsu techniques, which would make him stronger much earlier in his life.
Well, if Naruto and Hinata go to the past in fanfiction, it could be really interesting. They could meet their younger selves. Naruto might see his lonely childhood self and try to give him some hope. Hinata could also see her shy younger self and perhaps encourage her to be more confident earlier. And they could also influence the relationships between other characters. For instance, they might help their friends' parents get together or something like that.
In such a fanfiction, Naruto could share his old ninja tales with Boruto. Maybe he'd tell about his battles against the Akatsuki. Boruto would be in awe, seeing his father in a new light.
They might try to change some past events. For example, Naruto could prevent some of the early tragedies in the village. Hinata might also get the chance to be more assertive earlier in her life, since she has Naruto by her side this time. They could also have an impact on the relationships between different ninja clans.
In such a fanfiction, Naruto could gain a deeper sense of self. His father might share stories of Naruto's mother, which would make Naruto feel more connected to his family. They could also team up to face some threats that existed in the past, strengthening their bond as father and son.