Well, he might start his own secret training. Away from Hogwarts, he could find a hidden place and train with some unknown but powerful wizards. This new training could give him different skills and powers that Hogwarts couldn't offer.
The Hogwarts community as a whole would be in shock. Harry is sort of a symbol of hope in the fight against the dark forces. His withdrawal could lead to a decrease in morale among the students and teachers, making them more vulnerable to threats. Also, the balance of power within the school could shift, as Harry has often been a key figure in dealing with various dangerous situations.
One possible reason could be that he feels overwhelmed by the constant danger at Hogwarts. In some fanfictions, the threats he faces, like from dark wizards or dark magic within the school, might push him to the point where he thinks leaving is the only way to keep himself and his friends safe.
They would probably be shocked at first. I mean, Hogwarts reading fanfiction? It's a strange concept. But then they might be really curious about what Hogwarts is reading. They could try to get their hands on the same fanfiction to see what all the fuss is about.
One possible reason could be that the author of the fanfiction wants to explore a different storyline. Maybe they want to show Harry facing challenges outside the familiar Hogwarts environment, like in the wizarding world at large or in Muggle society.
He might lose the support system he had at Hogwarts. His friends like Ron and Hermione would be separated from him, which could lead to changes in their relationships. They might have to find new ways to communicate and support each other.
Hermione is often a common character. She would be there to support Harry in his journey as the heir, using her vast knowledge of magic to help him understand the implications of his new status.
Well, he might start by using his knowledge of Hogwarts' secrets and passageways. He could keep an eye on Harry during classes and in the common areas. Maybe he'd also form alliances with other students or teachers who he trusts to help in the protection effort.
In the fanfiction world, Harry might be the heir to Hogwarts if there was some sort of magical pact made generations ago. For example, perhaps one of his ancestors had a special role in the creation or protection of Hogwarts, and this role was passed down through the family. It could also be that his unique magical abilities, like his ability to resist Voldemort's attacks from a young age, are signs of a deeper connection to Hogwarts itself. This connection could be what designates him as the heir in the fanfiction's plot.
The story could then shift focus to Harry's adventures outside of Hogwarts. He could discover new magical places and meet different kinds of wizards. His departure might also lead to some of his Hogwarts friends trying to find him, creating new storylines about their search and the challenges they face along the way.