In this kind of fanfiction, Natsu might have some really interesting interactions. He could try to warn his past self about future challenges or mistakes. For example, he might tell his younger self about a particularly difficult battle and how to better prepare for it.
Well, it could start with Natsu accidentally stumbling upon a time - related magic or a magical artifact that transports him to the time when his past self exists. Then they would meet and there would be a moment of shock and confusion.
At first, it might be a bit tense. Natsu would be full of questions and his future self might be a bit reluctant to share everything. But as they start to talk, they could become more understanding of each other.
In the 'natsu meets his future self fanfiction', one possibility is that his future self warns him about certain events that are going to happen. For example, about an upcoming battle that is more dangerous than any he has faced before. His future self could also show Natsu new magic techniques that he will develop over time. It could also be a situation where Natsu's future self is not what he expected, perhaps having made some mistakes that Natsu now has the chance to avoid.
They could also have a philosophical discussion. Past Kratos has a lot of unresolved issues, especially regarding his past deeds. Future Kratos, having had more time to think about it all, could share his insights. For example, he might talk about how he has come to terms with his past and how past Kratos can start that journey too. This encounter could be a turning point for past Kratos's character development.
In the fanfiction, when Sasuke meets his past self, he might try to change the past. He could warn his younger self about the mistakes he made, like leaving the village and seeking revenge blindly. This encounter could be a chance for him to rewrite his own history and avoid all the pain and suffering he went through.
One possibility is that Ichigo could try to change certain events in his past. For example, he might want to prevent a tragedy that occurred or give himself some advice that would make his journey easier. He could also end up causing more chaos if he interferes too much, as small changes in the past can have big consequences in the future.
Maybe in this fanfiction, Natsu travels back in time on a quest to change a tragic event that happened in his past. When he encounters his younger self, he realizes how naive and impulsive he was back then. He starts teaching his younger self about the importance of self - control and strategy, which his younger self gradually starts to understand and apply.
His friends from the guild could be important. For example, Happy might be there to share in the joy of Natsu meeting his mother. Happy could also provide some comical relief during the emotional encounter.
The fanfiction might start with Natsu's search for his mother. When they meet, there could be some initial shock or disbelief. His mother could look at him with great love and pride. They might have a long conversation about his life so far, his friends, and his adventures. She could also introduce him to parts of his heritage that he was previously unaware of, which could shape his future actions and decisions in the story.