There could be some new characters as well. Maybe a mysterious wizard or witch who helps Harry on his way home. Or a group of young wizards who are also on their own journey and cross paths with Harry. Neville could be there too, showing how he has grown since the end of the main story and lending a hand to Harry.
Perhaps it's a story where Harry has been away on a secret mission, and his long journey home is filled with self - discovery. He might encounter old friends along the way who help him realize things about himself and his role in the wizarding world. He could also be haunted by memories of Voldemort during this journey, making it not just a physical but also a mental struggle.
One possible theme could be family. Since it's about being closer to home, family relationships, whether good or bad, might be explored. Another theme could be the contrast between the magical world and the normal world at home.
There could be some house - elves involved too. Maybe Dobby appears in the bathroom to offer Harry some help or advice, which would be a rather comical situation considering Harry is in the shower. Or other house - elves who are cleaning the bathroom while Harry is in there and he has some sort of interaction with them.
It could also include some of the Hogwarts professors as main characters. For example, Professor McGonagall, who has always been like a mother figure to Harry. Her wisdom and guidance would be crucial for Harry as he comes home to Hogwarts or the wizarding world in general. And Dumbledore, even if he's passed away, his influence could still be felt strongly throughout the fanfiction.
Obviously, Harry Potter himself is a common character. His friends like Hermione Granger and Ron Weasley also often show up. They might accompany Harry on his journey or play important roles in the events that occur during his travels.
I don't know for sure since I haven't read it, but it could be a lone traveler.
Harry Potter might be a bit surprised. He'd probably think it's strange that people are writing about his friends' and his own relationships in such a different way. Hermione would likely be very interested in the writing style and how the authors are creating these new relationships. She might even take notes to improve her own writing. Ron would just laugh it off most of the time. He'd find it a bit odd but also funny.
Obviously, Harry Potter himself. There could also be a new character who is like a raven - guardian, someone who has been watching over Harry because of his raven heritage. And perhaps some old characters like Hermione and Ron might play a role in helping Harry understand his new identity.
Harry Potter is the central character. There may be a wise old sea - turtle wizard who imparts important knowledge to Harry. Some sea - nymphs could be characters that either help or hinder Harry. Neville could also be part of the story, perhaps using his plant - based magic in a new way underwater to help Harry in his quest to be the king of the sea.
Obviously, Harry Potter himself. Then there would be his friends like Ron and Hermione. They would be there to support Harry and also be amazed by his new powers. Dumbledore would surely be in the story as he is an important figure in Harry's life. And of course, the villains like Voldemort and his Death Eaters who would be the antagonists against Harry's newfound abilities.