In the 'ash becomes a girl fanfic', perhaps the story focuses on how Ash, now a girl, tries to prove herself in a world that is often male - dominated in the Pokémon universe. She may face discrimination or disbelief from some trainers, but she uses her unique perspective and skills, developed from her previous experiences as a boy, to overcome these obstacles and become an even more successful Pokémon trainer.
Well, it could be about Ash waking up one day as a girl and having to deal with all the changes in his, now her, life. Maybe she has to adjust to new social dynamics, different reactions from friends and rivals, and also how to handle Pokémon battles in a different body.
In this fanfic, it could be that Ash is turned into Pikachu as a result of an experiment gone wrong. As Pikachu, he discovers new abilities and senses that he didn't know about before. He might form closer bonds with other Pikachu in the wild and learn their ways of living. He could also have to face challenges like being hunted by other Pokémon that see him as an easy target, and he has to use his new Pikachu - like skills to survive and try to find a way to turn back into his human form.
Perhaps the story could involve Ash being transformed into a Pokémon through some magical or scientific experiment gone wrong. As a Pokémon, he would join a group of other Pokémon on a journey. He might face challenges like being hunted by Pokémon hunters or having to prove himself to a Pokémon tribe. Along the way, he'd also learn about the different perspectives of Pokémon in their own world.
Pikachu would definitely still be there. It's Ash's most loyal companion, and it would be interesting to see how their relationship might change now that Ash is a girl. Maybe Pikachu would be more protective or show a different kind of affection.
In a 'sans becomes a girl fanfic', perhaps Sans - now a girl - decides to use this new form to her advantage. She could try to infiltrate a group that was previously only male - dominated in the Underground. This would lead to a whole series of adventures as she tries to keep her true identity a secret while achieving her goals.
Well, it could be about Ben 10 being transformed into a girl and then having to deal with the differences in how society treats him/her. Maybe he/she has to face new challenges in using the Omnitrix while being a girl.
Well, it could be about Gohan's daily life experiences as a girl. Maybe he has to deal with different social situations, like how his friends and family react to his new form.
In the 'izuku becomes a girl fanfic', perhaps the plot involves Izuku adjusting to her new physical form. She might struggle with things like different clothing styles and how society views girls in the hero world. Also, her relationship with other characters could change. Her friendship with Ochaco might become more complex as they now have more in common as girls. And Bakugo might react in a really interesting way, either being more protective or even more competitive towards her.
Well, perhaps the story could be about Harry suddenly waking up in a girl's body. He might struggle with the new physical appearance and how people around him react. For example, his friends might be really confused at first.
In this 'natsu becomes a girl fanfic', it could center around the idea that Natsu as a girl discovers a whole new side of the magical world. Since he is now a girl, he might be able to access certain areas or knowledge that were previously off - limits. He could also form new relationships with other characters who see him in a different light.
Well, perhaps in the fanfic, Ash turns into a girl because of a curse. As a girl, Ash could start to see the Pokemon world from a different perspective. Maybe she would form new relationships with her friends, like Pikachu being more protective. And she might have to enter Pokemon contests instead of battles at first due to the new appearance, but then find a way to get back into battles and show that she's still the same strong trainer inside.