One reason could be to escape the constant media attention and pressure that comes with being in the wizarding world's spotlight. Harry especially has always had the eyes of the public on him, and running away might be a way to get some peace.
The remaining Death Eaters could be the antagonists. Even though Voldemort is gone, there could be some who still hold a grudge against Harry and want to finish what their master started. They might track Harry and Ginny down as they run away, creating dangerous situations for the couple.
One possible plot could be that they run away to escape some dark magic threat that Voldemort's remaining followers are planning. They might go into hiding in a remote wizarding village, where they have to learn to fend for themselves without the help of the Order of the Phoenix. Along the way, they could discover new magical abilities or ancient spells that help them in their fight against the dark forces.
They might choose to run away secretly because they want to be alone together. They are in love, and the hustle and bustle of Hogwarts life doesn't give them enough privacy. So, they run away to a quiet place where they can enjoy each other's company without any interruptions.
Well, one possible plot could be that they run away to escape some sort of dark threat at Hogwarts. Maybe a new dark wizard has emerged and they feel that the school is no longer safe. So, they secretly gather some supplies, use magic to disguise their departure, and head off to a remote location like a hidden wizarding village in the mountains. There they try to find a way to fight the threat from afar while also exploring their relationship in a more private setting.
One possible plot could be that they run away to escape the chaos of the wizarding world. Maybe they are tired of the constant danger and politics. They find a secluded place, perhaps a hidden cottage in the Forbidden Forest. There, they start to build a new life together, learning magic in their own way, away from the prying eyes of Hogwarts and the Ministry. They might also discover new magical creatures and spells in their self - imposed exile.
Harry and Daphne are the main characters. Harry, who has been through so much in his life at Hogwarts and in the fight against the Dark Arts. Daphne, on the other hand, could be a character who is initially a bit of an enigma. As the story progresses, we might learn more about her motives for running away with Harry. Is it love? Adventure? Or something else entirely? Their interactions and how they adapt to being on the run are what will drive the fanfiction.
Well, they might run away to a secluded forest. There, they could build a small cabin and start a new life away from the chaos of their normal world. Maybe they discover some magical creatures in the forest that help them survive.
One reason could be to escape the public spotlight. After the war, Harry is a hero and Ginny is his girlfriend. They might feel overwhelmed by all the attention and want a quiet life, so they run away.