In a fanfic, Hermione might initially be in denial. She would keep expecting Harry to return any day. She would go to their old haunts in Hogwarts, like the library or the Gryffindor common room, and just sit there, reminiscing. As time passes, she realizes she has to move on. She starts teaching at Hogwarts and imparts her knowledge and the values Harry also held dear to the new generation of students.
Another scenario in the fanfic could be that Hermione starts to mentor young witches and wizards. She wants to pass on the things she learned from her adventures with Harry. She could be very strict with them, because she doesn't want them to make the same mistakes she and Harry did. At the same time, she's always secretly hoping that one of these young students will have some idea on how to get Harry back.
Some might be shocked and feel betrayed. Harry is a hero to many, so his departure could leave them feeling abandoned. Others might understand his need for a break and respect his decision.
Some might be in shock. After all, Harry has been such an important figure in the wizarding world for so long. His friends like Hermione and Ron would probably be very worried about him and try to find out where he went. The Ministry of Magic could be in a panic, fearing that without Harry, they'll be vulnerable to new threats.
Well, it could cause quite a stir in the wizarding world. First, the relationship between Harry and Draco has always been complex and full of rivalry. If Harry leaves Draco for Ginny, the Malfoy family might feel a sense of victory in a strange way, as Draco has been in this sort of unspoken competition with Harry. For Ginny, it would be a big step forward in her relationship with Harry. And among their friends, like Hermione and Ron, they might have mixed feelings. Hermione might be worried about how this would change the dynamics among them all, while Ron would probably be more focused on how it affects Harry's happiness.
There's also 'Farewell to Magic' in which fem Harry leaves after a big magical war. She realizes that the wizarding world has changed too much and she can no longer find her place there. So she travels far away to a place where magic is just a faint memory and builds a new life from scratch. She has to learn how to adapt to a completely non - magical environment which is full of challenges but also new opportunities.
Some authors write it because they want to explore different character arcs. Harry's character is so iconic in the original series. By making Harry female and having her leave the wizarding world, they can create new and unique storylines that deviate from the traditional narrative.
One possible reason could be the trauma he has faced. Harry has endured a great deal of pain, from the loss of his parents to the constant battles and threats in the wizarding world. He might want to escape all that and find peace away from it.
It could cause a great deal of shock and gossip. The Weasley family, especially Bill's siblings, would likely be very angry and confused. There might be a rift between the Weasleys and Fleur, and perhaps even some tension between the Weasleys and Harry. After all, Bill is a well - liked member of the wizarding community.
It could be that in the fanfic, Harry Potter discovers some deep - seated secrets about the wizarding world's power structure. Feeling betrayed, he decides to take extreme actions to expose and destroy it. For example, if he finds out that the Ministry of Magic has been using unethical means to control the wizarding population, he might use his influence and magic to bring it all crashing down. He could start by revealing the truth to the public, which could lead to chaos and the destruction of the established order in the wizarding world.