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.
Dumbledore might also play a role. He was always a guiding force in Harry's life in the original series. In this fanfic, he could be the one who sets up the training regime for Harry or gives him important advice about his training. His wisdom and power would add depth to the story and help Harry on his journey of training hard.
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.
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 aspect could be the character development. In fanfics, authors often explore different sides of the characters. Maybe in 'harry potter trains hard fanfic', we get to see Harry Potter training in ways that were not shown in the original books, like developing new spells or combat skills. This can give a fresh perspective on his growth as a wizard.
Obviously, Sakura is one of the main characters since it's about her training hard. There might also be her trainer, who could be an experienced and wise figure guiding her through the training process.
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, 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.
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.
Well, one interesting aspect could be the unique take on the Hogwarts Express. Maybe it's given some extraordinary abilities or a different role in the fanfic's plot. For example, it could be a magical portal to other dimensions rather than just a means of transportation to school.
One possible plot could be that Dr Strange is summoned to Hogwarts to train the students in advanced magic. He starts with Harry Potter, teaching him how to better control his magic and use it in more creative ways, like using time - based spells.
Obviously, Lucy is one of the main characters. And the dragons would also be main characters as she is training with them.