Harry is the central figure, but there might be some new characters introduced in the fanfic. For example, an old wizard who lives on the outskirts of Hogwarts and has some unique knowledge about magic that Harry discovers. This character could become a sort of mentor, even if from a distance, as Harry trains himself using the knowledge he imparts. Also, there could be antagonists like some students who are jealous of Harry's self - improvement and try to disrupt his training.
There could also be new characters introduced in the fanfic. Maybe a new mentor figure who guides Harry in his training. This character could have unique magical abilities and knowledge that they pass on to Harry. Another possibility is an antagonist who tries to disrupt Harry's training for some reason, adding conflict to the story.
I'm not sure specifically as it depends on the author of the fanfic. But it could include the classic Harry Potter characters like Harry, Hermione, and Ron. They might be on the train for some special reason related to their fight against Voldemort or some other new threat.
One interesting plot could be Harry finding unique ways to practice magic in isolation. For example, he might discover a hidden corner of the Hogwarts grounds where he can train without distractions. He could be experimenting with spells that are not typically taught in class, pushing the boundaries of his magical abilities.
Of course, there are often original characters in Harry Potter trains fanfiction. These could be new students who have their own secrets or powers. They might interact with the well - known characters, and sometimes they can even be the key to solving a mystery on the train, like uncovering a plot against Hogwarts that starts on the Hogwarts Express.
Obviously, Ash himself is the central character. His Pikachu is also often prominently featured, as it's his most iconic Pokemon. Sometimes, his other Pokemon like Charizard or Greninja might also play important roles in his self - training journey, either as partners in training or as sources of inspiration for him.
Obviously, Harry Potter himself is a main character. Since it's about him being alone on the train, he is the central focus. But sometimes, other characters like Dumbledore might make an appearance in his thoughts or as a sort of guiding force. For example, Harry could be reminiscing about Dumbledore's advice while on the train.
Obviously, the main characters are Kurenai and Sakura. Kurenai is the trainer and Sakura is the one being trained.
Obviously, Lucy is one of the main characters. And the dragons would also be main characters as she is training with them.
Obviously, Harry Potter himself is the main character. He is the one who is teaching himself potions.
Hermione Granger is very influential. She is extremely intelligent and well - read. She often helps Harry and Ron with her vast knowledge of magic, and her determination and loyalty contribute a great deal to their adventures and the fight against evil.