In this fanfiction, Harry could be alone because he feels estranged from his friends who have moved on with their lives in different ways. So he takes on a solitary mission to protect the wizarding world in the shadows. He becomes a sort of unseen guardian, constantly thwarting small threats that could potentially grow into big problems, all while dealing with his own loneliness and the memories of the war.
A potential character could be a reclusive old wizard who lives on the outskirts of the wizarding world. This wizard might have his own reasons for living in seclusion, but when he sees Harry's loneliness, he takes him under his wing. Another character could be a young, orphaned witch who is also trying to find her place in the post - war wizarding world and she crosses paths with Harry.
One possible storyline could be Harry struggling with PTSD from the war. He might isolate himself in Grimmauld Place, haunted by the memories of those he lost. Another could be him trying to find a new purpose in life, perhaps traveling the wizarding world alone to discover forgotten magic. Or he could be dealing with the public's perception of him as the 'Chosen One' and feeling the pressure to always be strong and heroic.
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.
Maybe in this fanfiction, Naruto is alone after the war because the villagers still don't fully trust him despite his heroic deeds. He then embarks on a journey to find a new purpose, away from the village that he once fought so hard to protect. Along the way, he discovers new powers within himself and also meets some unlikely allies who help him come to terms with his situation.
He could meet an old enemy who has also changed after the war. This enemy might now be in a similar situation of being alone and they could form an unexpected bond as they understand each other's isolation.
Harry could become an Auror, as he's always been good at fighting dark forces. Ginny, on the other hand, might continue her career in Quidditch. They would support each other's choices. Harry would cheer for Ginny at her matches, and Ginny would be proud of Harry for his work in keeping the wizarding world safe.
He might become very self - reliant. Since he has no one to depend on, he learns to take care of himself in every aspect, like finding his own place to live and getting food. He could also start to study magic more independently, exploring areas that were previously forbidden or not well - known.
One possible story could be that after the war, Harry suffers from paraplegia due to some dark magic he endured during the final battle. Ginny stays by his side, being his strength. She helps him through the difficult process of physical therapy. Their love becomes even deeper as they face this new challenge together.
One possible storyline could be Percy struggling with PTSD. He might have nightmares about the war and find it hard to reintegrate into normal life. For example, he could avoid social situations because the noise and crowds remind him of the chaos of the battlefield.