It could be a time - traveling version of Orochimaru. He might have his own plans for the past and Sasuke's interference could put them at risk. So, he tries to stop Sasuke from changing the past in a way that would undermine his future goals.
One idea could be that Sasuke goes back in time and tries to prevent the Uchiha massacre. He could use his knowledge of the future to stop Itachi from carrying out the order. Another could be that he goes back to his early days at the ninja academy and tries to change his relationship with Naruto from the start. Maybe he would be more open and friendly, which could change the whole dynamic of their rivalry.
She could meet her younger self. This would be an interesting encounter as she could offer advice and guidance to her younger version. Maybe she could help her younger self to be less afraid of her powers.
The concept of Sakura going back in time in relation to Sasuke in a fanfiction offers a great opportunity for character growth. Sakura could go back and train with Sasuke from an earlier age. This would not only strengthen their bond but also make Sasuke more open to Sakura's presence. It could also mean that Sakura becomes a more powerful ninja in this new timeline, being able to stand beside Sasuke as an equal rather than always chasing after him.
Perhaps Sasuke goes back to the very beginning of his ninja training. He decides to learn different jutsu that he didn't focus on before. He could also try to understand the political situation of the village better. Since he has seen the consequences of certain actions in the future, he aims to change things for the better. For example, he might try to improve relations between the Uchiha and the rest of the village much earlier. This would involve interacting with the elders and trying to find a compromise. It could also lead to a different path for Itachi as well.
He could change the course of major events. For example, he might prevent the rise of a powerful villain. This would have a huge impact on the entire galaxy. Maybe he could save some characters who died in the original timeline.
One interesting aspect could be that Luke goes back to a time when the Sith were just emerging. He could try to root out the Sith threat before it became as powerful as it did. He might have to be very careful not to disrupt the timeline too much, but his Jedi wisdom could be a great asset in this time - traveling adventure.
In this fanfiction, Sora might change key events. Maybe he could prevent some of the tragedies that occurred in the original story. For example, he could save a character who was lost before.
One possible plot could be that Kagome goes back in time and tries to change a major event in the past. For example, she might try to prevent a big battle that had a lot of casualties. She could use her modern knowledge and skills to her advantage in the past, like using first - aid knowledge to save lives.
She might change important events in the wizarding world. For example, she could prevent certain dark magic incidents or save characters who died in the original timeline.