Well, it could be that Naruto is cursed by a strange jutsu during a mission. Turning into a girl, he first has a hard time getting used to his new body. His friends initially don't recognize him. But then they notice some of his old mannerisms. He might then use his new form to his advantage, like getting closer to some female characters who were previously guarded around him and learning their secrets.
In a fanfiction like this, Naruto could turn into a girl as part of a training exercise gone wrong. His new female form makes him see the world from a different perspective. He realizes how differently people treat him now. Some guys start hitting on him, which he finds really annoying at first. But as time passes, he starts to understand the female experience better and uses this new understanding to become a better ninja and a more empathetic person in general.
One possible plot could be that Naruto turns into a girl to infiltrate an all - female organization that is suspected of having ties to a new threat. As a girl, he has to deal with the different social dynamics among the women, like cattiness in some cases but also strong sisterly bonds. He also has to hide his true identity while trying to gather information.
One possible plot is that Naruto, now a girl, enters a yuri - themed ninja tournament. There, she meets a powerful and beautiful female ninja. They start off as rivals but as they face each other in battles and training sessions, their relationship evolves into something more. Naruto's new - found femininity could add a whole new dynamic to their interactions.
Maybe it's a self - discovery plot. Naruto has always felt a special connection to the Nine - Tails. One day, due to some internal spiritual awakening, Naruto starts to transform into a fox girl. This transformation makes Naruto re - evaluate his identity. He starts to explore the more feminine side of his personality and the hidden powers that come with the fox girl form. Along the way, he also helps other characters in Konoha understand that there's more to a person than their physical appearance, and his new form becomes a symbol of acceptance and change in the village.
Well, one possible plot could be that Kushina uses some sort of jutsu by mistake that turns Naruto into a girl. Naruto then has to deal with all the new experiences like how people treat him/her differently. He/She might also struggle with adapting to new clothing styles and social expectations in the ninja world.
It could be that Kurama's power goes out of control and accidentally turns Naruto into a fox girl. Naruto then has to search for a way to fix it. In the process, he might discover new aspects of Kurama's power. He could also meet some old enemies who don't recognize him in this new form and this could lead to some interesting encounters. Naruto would also have to deal with the cultural and social implications of being a fox girl in the ninja world, such as how he is treated differently by different clans.
One possible plot could be that Sasuke uses some kind of rare jutsu accidentally while sparring with Naruto. This jutsu has the side effect of changing Naruto's gender. At first, Naruto is shocked and confused. But then, he (now she) starts to discover new aspects of the ninja world as a girl. For example, she might notice how differently she is treated by some of the male ninja. And Sasuke, feeling guilty, tries to find a way to reverse the effect while also protecting Naruto from any potential harm that could come from this new form.
A possible plot could focus on how Tails' daily life changes. As a girl, she might have to deal with different social expectations. Her hobbies and interests could shift slightly. For example, she might be more interested in certain types of fashion or more nurturing activities. Her relationship with Amy could also change, perhaps they become closer friends as they share more 'girly' things. And Tails' mechanical skills might be seen in a new light, as she uses them in a different way to solve problems in her new form.
Well, one possible plot could be that Sans somehow gets hit by a strange magic spell. As a girl, he/she might struggle to fit into the existing relationships in the Underground. For example, Papyrus might be really confused at first but then tries to be supportive. And Sans (as a girl) could also have different interactions with Frisk, like maybe a more motherly or sisterly bond.
Well, perhaps in the fanfiction, Ash is exposed to a mysterious Pokémon's special ability that causes the transformation. As a girl, Ash discovers new aspects of himself. He might find that some Pokémon are more attracted to his new form and are more willing to be caught or trained. He could also use this new identity to his advantage in battles, like using the element of surprise against opponents who are used to facing the male Ash.
In a fanfiction where Nagisa turns into a girl, it could be part of a wish - fulfillment scenario. Nagisa secretly wished to experience life as a girl for a day, and some supernatural being grants that wish. As a girl, Nagisa has to navigate through daily life, school, and social situations. There could be humorous moments when Nagisa tries to act like a girl but still has some of the old habits from being a boy, like being too rough during sports in a girl's body.
Well, in a Todoroki turns into a girl fanfiction, perhaps there's a villain who has a transformation quirk and uses it on Todoroki as a form of psychological warfare. Todoroki, now a girl, has to find a way to reverse the effect. In the process, he/she realizes that society treats female heroes differently and has to fight against those prejudices too. Maybe he/she even uses this new form to her advantage in some battles, by using the element of surprise.