Obviously, Hadrian is one of the main characters. He is the version of Harry Potter with a different name. Then, we might still see characters like Hermione and Ron. They would interact with Hadrian in different ways compared to how they interacted with Harry. Their relationships could be more complex or different in nature.
There could also be some original characters in the fanfiction. For example, a new teacher at Hogwarts who has a special connection with Hadrian. Or perhaps a mysterious wizard from another land who comes to Hogwarts because of Hadrian. These new characters could add more depth and variety to the story.
Dumbledore would also be a main character. His relationship with Hadrian could be a key part of the story. He might have different expectations of Hadrian or might be more or less involved in his life depending on the fanfiction. And of course, the villains like Voldemort would still be there. Hadrian's battles against Voldemort could be very different from Harry's, with different strategies and outcomes.
Hadrian is the central figure in most of these fanfictions. He is usually depicted as a more complex or altered version of Harry. Voldemort can also be a significant character, as the main antagonist in the Harry Potter universe. In some fanfictions, new characters are introduced who play important roles in Hadrian's life, such as a mysterious mentor or a rival wizard. Snape might also be there, his relationship with Hadrian being a key aspect in some stories.
One interesting plotline could be how Hadrian deals with the expectations of the wizarding world differently from Harry. Maybe he uses his knowledge of the future in a more proactive way to change things for the better in Hogwarts, like reforming the House system.
Hermione Granger could also be a prominent character. She would use her vast knowledge to research about the history and magic associated with the wall. For instance, she might be the one to find ancient texts that mention the wall's significance in the wizarding world. And then she would share this knowledge with Harry and Ron to start an adventure related to it.
There could be a group of Japanese students who are initially skeptical of Harry but later become his allies. For example, a shy girl who is really good at Japanese magic but lacks confidence. And a tough - looking boy who is actually very kind-hearted and they all form a sort of magical study group together with Harry. There might also be a mischievous Japanese magical creature that befriends Harry and causes some chaos in the school.
Obviously, Harry Potter himself is the central character. Hermione and Ron would most likely be involved too. They would probably try to find a way to get Harry out of Azkaban. Dumbledore might also play a role, perhaps guiding Hermione and Ron from behind the scenes or even trying to influence the wizarding court to re - evaluate Harry's case.
Obviously, Harry Potter himself would be the central character as the title implies. Hermione and Ron would most likely be involved as well, since they are Harry's closest friends. They would probably be the ones trying to figure out what's wrong with Harry and how to fix him. Dumbledore could also play a big role, as he often has the wisdom and power to deal with strange situations.
Obviously, Harry Potter himself. And there could be characters like Hermione and Ron who might either go with him or be involved in some way from afar. There may also be original characters created for Alfe, such as an Alfe wizard who becomes Harry's guide.
Obviously, Harry Potter himself. Then there could be Hermione and Ron, who might visit him at Harvard or communicate with him via magic. There could also be new characters like his Harvard roommate, who could be a normal Muggle but start to suspect that Harry is not an ordinary guy. And maybe some professors at Harvard who take an interest in Harry's different way of thinking.
There could be a young Salem witch named Lily. She befriends Fem Harry Potter and shows her around Salem. Lily could be very knowledgeable about the local magic and help Fem Harry Potter understand the differences between Hogwarts magic and Salem magic.
Neville Longbottom can also be a main character in some 'Harry Potter goes back in time' fanfictions. Given his growth and importance in the original series, in the fanfic, Harry might go back and help Neville become more confident earlier. This could have a significant impact on the fight against Voldemort as Neville could then be an even more powerful ally from an earlier time.