In the 'Sora Goes Back in Time' fanfiction, Sora may run into his friends at different points in their lives. He could meet Riku when they were just kids, and see how their friendship started in a whole new light. He might also come across Kairi at a crucial moment in her past, and his presence could change the way she develops as a character. There could also be encounters with other minor characters from the original story, whose roles could be expanded upon in this time - traveling scenario.
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.
If Sora goes back in time in fanfiction, it could be a chance for him to gain new powers or knowledge. He might meet his younger self and teach him things, or he could discover secrets about the Keyblade that were lost over time. This could make him even stronger in his own time and better equipped to face the Heartless and other enemies.
Goku might run into past versions of his friends. He could see a younger Krillin or Bulma and have some really interesting interactions. He could also meet past versions of his enemies and try to change their fates. For instance, he could meet a young Vegeta and try to steer him away from the path of evil. This would be a huge change in the Saiyan's story.
She might meet her younger self. This could be a really strange encounter as she tries to understand how she used to be.
Maybe it's an old foe who has managed to regain power and wants to make Sora pay for past defeats. For example, a powerful dark sorcerer who was once defeated by Sora but has now found a way to capture him through some devious plot.
He might meet Luke before he turned bad. Percy could try to change Luke's fate, convince him not to follow Kronos. It would be a great chance to save a friend and prevent a lot of the chaos that happened later.
He might meet a younger version of Alfred. Alfred has always been an important figure in the Wayne family and Damian could learn a lot from him, or even try to give him some hints about the future. Also, he could run into a younger Commissioner Gordon. Their interactions could be really interesting as Gordon is such an important ally of Batman.
There's no way to tell for sure who Nomura Sora is based on this phrase alone. It could be an ordinary person whose story has been told and is now over, but more likely, given the somewhat cryptic nature, it's a fictional character from a story. Maybe it's a character from a Japanese - themed story, considering 'Nomura' is a common Japanese surname, but that's just speculation without further context.
Sora is likely a character created within the fanfic world. He could be a powerful shinobi with unique abilities that Naruto can learn from. Maybe he has a special chakra nature or some extraordinary combat skills.
Bella could meet an old neighbor. This neighbor might tell her about the changes in the neighborhood over the years. Maybe there are new families, new stores, or even some interesting local events that she has missed. It would be a great way to bring a sense of familiarity and newness to the story at the same time.