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 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.
It could develop in a really interesting way. Since Naruto is from the future, he might have knowledge that he uses to protect Kakashi. This would make Kakashi curious about Naruto. As they interact more, they could start to develop a deep bond. Naruto might share some of his future experiences with Kakashi in a veiled way, and Kakashi would start to see Naruto in a different light, leading to a relationship that is based on mutual respect and a bit of mystery.
The theme of friendship is also prevalent. Despite the time difference, they form a strong bond. They might start off as strangers, but as they work together towards a common goal, their friendship deepens. In some fanfictions, this friendship could even change the entire Naruto universe's future. Additionally, the theme of self - discovery is often explored. Naruto may learn more about his own roots and past through his interactions with Kakashi, and Kakashi may discover new aspects of himself with Naruto's influence.
In a future Naruto and Kakashi fanfiction, Naruto could gain the ability to communicate with all living things. This would help him in understanding the needs of the village and the surrounding nature. Kakashi, on the other hand, might develop a new Sharingan ability that allows him to see the future in a very limited way, like seeing the next move of his opponent a few seconds in advance. This would enhance his combat skills significantly.
One idea for this 'Past Kakashi Meets Future Obito' fanfiction could be that their meeting is not a coincidence. Maybe it's part of a grand plan by some mysterious force. When they meet, past Kakashi would be in awe of future Obito's power and skills. Future Obito, though, would see the innocence still in past Kakashi. They could end up training together, with future Obito teaching past Kakashi some new jutsu. And as they bond, they might rewrite their fates and change the future of the ninja world for the better.
In future Naruto and Kakashi fanfiction, their relationship could be one of mentorship still. Naruto, now a powerful Hokage, might seek Kakashi's wisdom on handling complex political situations in the village. Kakashi, with his years of experience, could offer valuable insights. They could also have a more equal friendship, sharing stories of their past adventures over a cup of tea.
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.
A cool plot twist could be that future Obito is actually there to stop past Kakashi from making a certain decision that would have far - reaching negative consequences. Another one might be that past Kakashi discovers that future Obito has a hidden agenda that is not what it seems at first.
They often use flashbacks. For example, when Naruto is facing a tough situation in the future part of the story, a flashback to his past training with Jiraiya can give him the inspiration to overcome it. This way, the past is directly linked to the future.