Obviously, Harry Potter himself would still be a key character. He was the hero of the war, and his influence would still be felt in the post - war world. He could be a guiding figure for the younger generation.
In the 'Harry Potter after the war story', perhaps Harry and his friends would focus on reforming the wizarding world's laws. There were a lot of unjust laws and practices that were brought to light during the war. They could work towards a more inclusive and fair society for all wizards and witches, regardless of blood status.
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.
I really like 'Eclipse'. It focuses on the rebuilding of Hogwarts and how the students and teachers are trying to move forward. It has some really interesting new relationships and character developments that are quite in line with the original Potterverse feel.
There are quite a few. 'Rebuilding the Wizarding World - After the War' is a fanfic that details the efforts of Harry and his friends to fix all the damage caused by the war. It has great descriptions of the rebuilding process. 'Harry Potter: Post - War Revelations' is a fanfic that uncovers some secrets that were buried during the war, which is quite exciting. And 'The After - War Journeys of the Golden Trio' focuses on the adventures and growth of Harry, Hermione, and Ron as they move forward in a post - war world.
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.
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.
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.