It could lead to a completely different character dynamic and story arc. Maybe she'd face different challenges and have a unique perspective on being a hero.
Well, one possible plot could be that Deku accidentally drinks a strange potion created by a villain. This potion has the side - effect of changing his gender to female. At first, he's shocked and confused. But then, he realizes that he can use this new form to his advantage in hero work. For example, he might be able to infiltrate a female - only villain group more easily. He also has to deal with his friends' reactions, some are surprised while others are supportive and help him adjust to his new body while still being a hero.
An AU fanfic is a type of fan fiction where the story takes place in an alternate universe with different settings or circumstances than the original work.
An au fanfic is a type of fan-written story that takes the characters or setting of an existing work and places them in an alternate universe or situation that differs from the original.
It could be a villain who is obsessed with creating chaos through strange transformations. This villain might have targeted Deku specifically because of his status as a rising hero. They want to see how Deku will cope with being turned into a girl and use it to undermine his confidence and hero image.
There are very few, if any, truly family - friendly fanfics with such a concept. The idea of a character getting a girl pregnant is often part of more mature or inappropriate storylines. However, some fanfic writers might take this concept and twist it into a more positive and educational story about responsibility and growing up, but these are rare.
One possible plot point is how Deku as a girl interacts with female characters. She could form new friendships or rivalries with them. For instance, she might bond more closely with Uraraka now that they share the same gender. And in terms of her hero training, she may face different challenges and opportunities compared to when she was male.
One interesting fanfiction could be where Deku dresses like a girl as part of a undercover mission in the hero world. He might use this disguise to gather information on a villain who is more likely to let their guard down around a female. This could lead to some really comical and exciting situations, like when his friends almost don't recognize him at first.
There could be a fanfiction where Deku dresses like a girl to enter a female - only hero training event (for some strange reason in the story's universe). This would put him in a unique position where he has to not only deal with the physical differences of the disguise but also the social and competitive aspects of the event. It could be a great story about him breaking gender barriers in the hero world while looking like a girl.