Maybe in the fanfic, Sakura turning into a child is part of a time - travel mishap. She gets sent back in time but her body regresses to a child's form. So she has to navigate the past world as a child, and along the way, she discovers things about her past self and the origin of her powers that she didn't know before. And she also has to find a way to get back to her own time and her normal age.
Well, one possible plot could be that Sakura is hit by a magic spell that turns her into a child. Her friends then have to figure out how to reverse the spell while also protecting her in her vulnerable state. They might take her to different magical places or consult with wise old sages to find a cure.
In the fanfic, it could be that Sakura is cursed by an enemy. As a child, she has to rely on her basic instincts and the little bit of magic she still has access to. Her friends are shocked at first but then they see this as an opportunity for Sakura to relearn some of her magic in a different way. They start teaching her simple spells again, and as she grows in this child form in terms of magical knowledge, she also gets closer to breaking the curse.
Obviously, Sakura herself would be a main character. Her friends like Naruto and Sasuke could also be main characters. Naruto might be the one who is overly excited and wants to play with child - Sakura all the time, while Sasuke would be more focused on finding a way to turn her back. Kakashi could also be involved as the mentor figure who guides them through the process.
The plot could revolve around Corrin trying to find a way to reverse the transformation. Along the way, they could encounter various challenges. For instance, they might have to go on a quest to find a rare ingredient for a potion that could potentially turn them back. Their child form could make it difficult to traverse dangerous terrains or face powerful enemies. However, they could also make new friends among the younger characters in the Fire Emblem world, who could help them in their journey.
One possible plot could be that Percy, as a child, has to navigate his newfound smallness while still having the memories of his older self. He might struggle to convince his friends that he is actually Percy, and they initially think it's some sort of trick. Then, he could use his knowledge from his older self to help them in a new and unexpected way, like solving a mystery that the younger versions of them couldn't figure out on their own.
In the fanfic, perhaps Goku's transformation into a girl is the result of a magical spell. As a girl, she might start to see the world from a different perspective. She could be more in touch with her emotions and this could either enhance or hinder her fighting abilities. For instance, she might be more empathetic towards her enemies, which could lead to some interesting moral dilemmas during fights. Her training regime might also change as she adapts to her new body.
One possible plot could be that Chihiro, after some kind of encounter with a powerful spirit or magic in the spirit world, gradually starts to transform into a spirit herself. She might first notice small changes like her body becoming more translucent. As she turns into a spirit, she could gain new abilities, such as the power to communicate with plants and animals in a way she couldn't before. She might also face challenges as the other spirits don't know how to react to her transformation. Some might be scared, while others might see her as a threat or an opportunity.
The plot of a Naruto turns into Sakura fanfiction could involve Naruto experiencing Sakura's emotions more directly. He might feel the pressure she has always felt to keep up with Naruto and Sasuke. This could lead to him understanding her better and trying to change things when he turns back. Also, there could be a situation where Naruto - as - Sakura has to go on a mission alone. This would force him to fully embrace Sakura's skills and personality. He could end up using her intelligence and strategic thinking in ways he never thought possible, which would not only be a growth for the 'Naruto - in - Sakura' character but also an interesting exploration of Sakura's potential.
Well, one possible plot could be that a villain uses a new type of quirk -altering device on Deku. As a child, he might have to rely on his basic knowledge of heroics and his natural determination. His friends would be confused at first but then quickly realize it's still Deku inside. They'd have to protect him from other villains who might see this as an opportunity to get rid of the future symbol of peace while he's vulnerable.
Perhaps in the fanfiction, when Touma turns into a child, he discovers a new side of the world he didn't notice before. As a child, he has a different perspective. Maybe he befriends other children who are in some sort of magical or dangerous situation, and his child form has unique powers to help them. The story could be about him growing and learning while in this child form.
One possible plot could be that a strange jutsu backfires on Sakura during a mission. This jutsu could be an experimental one that an enemy ninja uses. As a result, Sakura turns into a little girl. Naruto, being her friend, has to protect her in this vulnerable state. He might have to teach her basic ninja skills all over again as she has the mind and abilities of a little girl now.
The plot might be that Sakura has always wanted a family but couldn't have one in the normal way. One day, she comes across a child who has been abandoned. She instantly feels a connection and decides to adopt. Along the way, they bond over shared interests. For example, if Sakura likes gardening, she teaches the child about plants and they grow a beautiful garden together, strengthening their relationship.