She could run away because of a broken heart. Maybe she had a relationship that ended badly, and she needs to get away from the memories. In the process of running away, she could meet new people who help her heal and grow as a person. This type of storyline often explores the more vulnerable side of fem Tsuna.
She might be moving away because she wants to pursue a new opportunity, like a special school or a job in a different place.
One possible reason could be that he feels misunderstood by his family or friends. Maybe he has some secrets that he's afraid to share, and the fear of being judged makes him run away.
In some fanfictions, it could be that he has made a big mistake. For example, if his actions as Spider - Man led to the harm of an innocent person. He would be so guilt - ridden that he decides to run away from everything, including his friends and family in Queens.
Maybe Pikachu is feeling neglected by its trainer. If the trainer has been paying more attention to other Pokemon or is too busy with something else, Pikachu might decide to run away to get some attention.
Maybe they run away because they are tired of the constant danger at Hogwarts. They've faced so many threats, and they just want a break. So they run to a peaceful place where no one knows them.
One possible reason could be a conflict of values. Hermione is a strong advocate for justice and equality among wizards and non - wizards alike. Draco, on the other hand, was brought up in a family with pure - blood supremacist views. Hermione might run away from Draco in a fanfiction if she realizes that his views are unchangeable and they are fundamentally opposed to her own. For example, if Draco makes a derogatory comment about Muggle - borns in front of her, it could be the last straw and she decides to run away.
Maybe he wants to escape the constant danger in the UK wizarding world. Voldemort's followers might still be a threat even after his defeat, and France could seem like a safe haven.
Maybe he runs away because he's afraid for his family's safety. In fanfiction, it's possible that the Decepticons target Jack's family to get to him or the Autobots. To protect them, he decides to leave and lead the danger away from them. He thinks that by distancing himself, his loved ones will be safe.
One possible reason could be that he feels unsafe at Hogwarts. Maybe there are threats from dark wizards within the school that the teachers are unable to fully protect him from. Sirius, being his godfather, represents a safe haven.
There are fanfictions where fem Tsuna runs away after a big fight or argument. She might feel misunderstood and decides to leave to clear her head. For example, she could end up in a small, peaceful village where she starts a new life, learning valuable lessons about herself and the world around her. It often adds a new layer of character development to her.