Maybe Harry feels a sense of guilt. In the context of the war, he might think that he's failed in some way by getting into this unexpected situation. He could believe that his new condition might put others at risk or that he's no longer the hero everyone expects him to be. So, to protect others or to avoid the shame, he decides to run away.
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.
Some in the wizarding world might be very concerned. His friends, like Hermione and Ron, would probably be worried sick and immediately start looking for him. They would understand that he must be going through a lot and would be eager to help him through whatever he's facing.
Another reason could be that she wants to explore the world on her own terms. In the fanfiction, Mirabel may be tired of always being in the family's protective bubble. She desires to see what lies beyond the village and the mountains, so she runs away to start her own adventure.
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.
One possible reason could be fear. Minato is a very powerful shinobi, and Naruto might be scared of him for some reason. Maybe he has heard stories about Minato that made him afraid.
He could run to the Forbidden Forest. It's a place full of mystery and danger, but also a good hiding place as it's vast and not many people would expect him to be there. He might find some solace among the magical creatures there.
One reason could be the trauma he endured during the war. He witnessed so much death and destruction that he might feel the need to escape it all. Maybe he wants to get away from the constant reminders of his friends who didn't make it.
One reason could be fear. Snape has always been rather intimidating to Harry. Snape's cold demeanor and his past interactions with Harry's father might make Harry feel constantly on edge around him. So, running away could be an instinctual response to this fear.
There are several possible reasons. Firstly, a sense of being controlled. If Edward is constantly making decisions for her or restricting her actions, Bella would want to break free. Secondly, self - preservation. If she realizes that the relationship is putting her in more danger than she can handle, she'll run. Thirdly, a change in her feelings. Maybe she falls out of love with Edward or realizes she was never truly in love, but rather in some sort of infatuation. So, she runs away to sort out her emotions and her life.
One possible reason could be fear. Rin might be afraid of his own powers and the potential harm they could cause to Yukio. Since he cares about Yukio, he may choose to run away to protect him.