Often, in such a fanfiction, the story develops around the chaos that his transformation brings. Since Inuyasha is now a child, his usual brash and confident self is replaced with a more innocent and sometimes naïve version. This can lead to some comical situations, like trying to fight with a smaller body and less strength. His friends have to keep him out of trouble more than before, and there could be a plot where they search for a way to turn him back to normal.
Perhaps the cause of Kagome becoming a child in the fanfiction could be a cursed spell from a powerful demon. This demon might have wanted to weaken Kagome's powers as she was a threat. As a child, Kagome could have some child - like innocence and different abilities. For example, she might be able to communicate with certain spirits more easily because children are often seen as more pure in such fictional settings.
One common reason could be a spell gone wrong. Maybe an enemy casts a spell that was intended to weaken him but instead turns him into a child. Another reason might be some sort of magical accident. For example, he messes around with a powerful but unstable magical artifact and it has the unexpected consequence of changing his age.
In the fanfiction, Kagome's enemies could underestimate her. They think that because she's a child, she's not a threat. But in reality, even as a child, Kagome still has her strong will and some of her powers. She could surprise them by using her wits and the little bit of spiritual power she has left to outsmart them. For instance, she could lead them into a trap that her friends set up.
In the 'deku gets turned into a child fanfiction', it could lead to some really interesting storylines. Maybe he would see the world in a whole new way, with the innocence of a child. His interactions with his mentors could become more like a child - adult relationship where they have to guide him more. Also, his enemies might underestimate him at first, which could create some unique battle scenarios.
One potential storyline could be Naruto having to re - experience his early life with his new - found child self's perspective. He might struggle with the lack of strength he once had as an adult. For example, he could have trouble with basic ninja training again, but this time with the knowledge of his future self, which could lead to some interesting twists. Another could be how his relationships change. His friends might initially not recognize him and he has to prove his identity in a rather comical way. And also, the villains might underestimate him as a child, which could be a great advantage for Naruto to outwit them.
In a 'Seto gets turned into a child fanfiction', the plot might revolve around Seto's own struggle to adapt to his new form. He's used to being in control and powerful, but as a child, he has limited abilities. He could try to communicate with others about what happened to him, but with his child - like speech and behavior, it becomes a challenge. His friends might have to protect him from those who would take advantage of his vulnerable state.
In a fanfiction where Deadpool is turned into a child, his internal monologue would be hilarious. He'd probably still have all those wild thoughts running through his head, but they'd be filtered through a child's perspective. He might be more focused on things like getting ice cream or playing with toys, while also trying to figure out how to get back to his normal self. And his costume? It would probably be way too big for him, and he'd have to improvise, like using a belt to keep his pants from falling down, which would add to the comical effect.
In the 'deku gets turned into a child fanfiction', Deku is the main focus, but his friends like Uraraka and Iida would be key characters. Uraraka might be especially kind and motherly towards him. Iida could be strict in making sure Deku follows the right path. And villains like Shigaraki could see this as an opportunity to target Deku in a new way, so they would also be significant characters in this scenario.
The story could progress with Deadpool having to adapt to his new child form. He might start going to school in the fanfiction world. There, he could get into trouble for his unruly behavior that comes from his adult - like mindset in a child's body. Or he could make new friends who are actually kids and learn about the simple joys of childhood like building sandcastles or playing hopscotch.