Friendship might be a theme. The older Naruto could emphasize to his younger self the importance of his friends, like Sasuke, Sakura, and Kakashi. Also, the theme of destiny. The older Naruto can tell his younger self that he has a great destiny ahead and should keep striving for it. And it could be about forgiveness too, as Naruto has had to forgive many of his enemies throughout his journey.
Well, Naruto might try to give his younger self some advice. Maybe he'd tell him to train harder or to be more understanding of Sasuke earlier. It could be a really interesting scenario where the older Naruto tries to prevent some of the bad things that happened in his past from occurring again.
One interesting plot twist could be that the alternate Naruto is from a parallel universe where the roles of good and evil are reversed. This would force the real Naruto to question his own beliefs and values. And it might also lead to a battle between the two Narutos, not just a friendly encounter, as they fight over what is right and wrong.
In a fanfiction scenario where Naruto meets his younger self, it would be a very unique situation. Naruto might show his younger self some of the new jutsus he's mastered, like the Rasengan variations. His younger self would be eager to learn from him. Also, Naruto could talk to his younger self about his dreams and how he's still holding on to them, even after all the difficulties. This meeting could potentially change the course of his younger self's life, as he could be more determined to reach his goals faster with the knowledge of his future self.
One possible theme is self - discovery. The older Deku has already gone through a lot of growth, and by meeting his younger self, he can see how far he has come. The younger Deku can also start to understand his potential better.
If Naruto is sealed in his younger self in a fanfic, it could be chaotic. His chakra control might go haywire as his younger body tries to adapt to the sealed future self. The village elders might notice something strange and try to investigate. His training with Iruka Sensei could take a whole new turn as he might show advanced skills too early. This could also have an impact on the Nine - Tails within him. The Nine - Tails might react differently to this new situation, perhaps becoming more or less aggressive depending on how the seal affects Naruto's mental state.
In this fanfic, Naruto might teach his younger self some advanced jutsu. For example, he could show the younger Naruto how to better control the chakra for Rasengan at an earlier stage. This would make the younger Naruto stronger faster in the story.
In this fanfic, Naruto might use his time - traveling jutsu accidentally. He could then see his younger self in a dangerous situation, like being attacked by a powerful enemy. So, he jumps in to save him, using all his advanced skills and knowledge. Maybe he also gives some important advice to his younger self to avoid future mistakes.
Well, in such a fanfic, Naruto might initially be confused. He could start comparing his own life experiences with those of his alternate self. Maybe they would exchange stories about their training, friends, and enemies.
In this fanfiction, Percy might be shocked at first to see his younger self. He could offer advice to his younger version, like how to better handle the challenges in the magical world. Maybe he'd warn his younger self about certain enemies or mistakes he made in the past.
Well, it could be that Deku's younger self is initially in awe of his future self. They might start training together, with the older Deku showing the younger one new moves and ways to improve his skills. Also, the older Deku could tell stories about his battles and how he overcame various villains, which would give the younger Deku more confidence.