Well, one possible scenario is that Ichigo could try to warn his younger self about the upcoming battles and hardships. He might give some tips on how to better control his powers from the start, which could potentially change the course of his journey in the original story.
Their powers might interact in a very chaotic way. Since Ichigo's powers have evolved over time, his older self's more refined and powerful reiatsu could either overshadow or disrupt his younger self's still - developing powers. It could be like a clash of two similar but not exactly the same energy sources.
In this fanfiction concept, the interaction of their powers is quite interesting. Since Ichigo's power has evolved over time, his past self may have a purer, more instinctual form of his abilities. When they meet, the future Ichigo's power, which has been through more battles and growth, could act as a catalyst for the past Ichigo's power. It could be like a spark that ignites a new level of understanding and control for the younger Ichigo. On the other hand, the past Ichigo's power, which is still in a more nascent state, might reawaken a sense of rawness in the future Ichigo's power. This could lead to the discovery of new techniques or a different way of using his existing powers for both versions of Ichigo.
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.
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.
In this fanfiction, Natsu's older self might have a better understanding of the consequences of his actions. When he meets his younger self, he can show him how certain choices in the past led to both good and bad outcomes. This would make the younger Natsu more cautious and thoughtful. Also, the younger Natsu's innocence and enthusiasm could remind the older Natsu of his lost youth, making him regain some of his earlier passion. Overall, both versions of Natsu would grow and change through their interactions.
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.
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.
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.
One great Ichigo time travel fanfiction is 'A Time - Twisted Adventure'. It takes Ichigo to different points in the Bleach timeline in unexpected ways. The character development is really interesting as he has to adapt to the past or future situations while still holding onto his core values.