It could be Ron. Maybe he starts to feel that Harry has changed too much after the war and is no longer the friend he once knew. He might be influenced by outside forces or his own insecurities. Another possibility is Hermione. If she gets too involved in the new Ministry politics and starts to believe that Harry's actions are not in line with the new wizarding order, she could turn on him.
Perhaps Harry meets magical creatures that are rarely seen by wizards. Since he is out exploring after the war, he might stumble upon a group of centaurs who have their own unique wisdom about magic and the future. He could also encounter veelas, and through his interactions with them, learn more about the different cultures within the magical world. There's also a chance he meets other young wizards who are on their own adventures, and they form a sort of traveling group together.
In such a fanfiction, Harry might initially struggle with his blindness. Ginny, being the strong - willed character she is, would encourage him to not let it hold him back. There could be a lot of emotional moments between them, like when Harry first realizes he can no longer see Ginny's beautiful face. Ginny, on the other hand, would assure him that their love is not based on sight. They might also encounter difficulties from the wizarding society that doesn't fully understand how to deal with a war - hero - turned - disabled, but they would face it all together.
In Harry Potter fanfiction, life after war could be a time of rebuilding. The wizarding world might focus on restoring Hogwarts to its former glory. Wizards and witches would come together to repair the damaged parts of the school, like the Great Hall which may have been scarred during the battles. They would also work on mending relationships. For example, some families who were on opposite sides during the war would try to reconcile. And there could be new magical laws and regulations to prevent another such dark time from occurring.
One possible reason could be that he is suffering from post - traumatic stress disorder. After all he has been through, he might want to isolate himself from the wizarding world to heal. Another reason could be that he feels a sense of guilt for those who died in the war, and disappearing is his way of punishing himself.
There could be a story focused on the relationships that form after the war. For example, Neville and Luna might start a magical plant research project together, and their friendship could deepen into something more romantic over time as they work side by side.
One interesting plot could be about the rebuilding of Hogwarts. Maybe the characters come together to restore the damaged parts of the school, using magic in creative ways. They might also find hidden secrets during the rebuilding process.
His character would likely become more introspective. Without his friends always around, he'd have to face his inner thoughts and feelings. He might become more self - reliant and learn to trust his own judgment even more.
Harry might finally find some peace. He could focus on his studies or start a new career in the wizarding world. As for Tonks, she might be more involved in rebuilding the Order of the Phoenix or helping to improve the security of the wizarding community. Their lives would be less centered around the fight against evil.
The characters' development after the war can be quite complex. Luna Lovegood might start a movement to make the wizarding world more accepting of different beliefs and oddities. She could use her unique perspective to bring about a more inclusive environment. Seamus Finnigan could become an advocate for Muggle - born rights, having witnessed the discrimination during the war. And the older generation, like McGonagall, would have to adapt to a new world order. She would need to balance her traditional values with the need for change, guiding Hogwarts and its students into this new era of post - war wizarding life.