He might do it for a bet. Just like some friends might bet on who can pull off a crazy stunt, his friends could have bet him that he can't dress like a girl and act the part for a certain period.
Perhaps in the fanfiction, Izuku is dared by his friends to dress like a girl for a day. This could lead to all sorts of comical situations, like getting hit on by guys who don't realize he's a boy, or having trouble doing normal boy - related activities while in girl's clothing.
Obviously, Naruto would be the main character since the title focuses on him dressing like a girl. His friends like Sasuke and Sakura are also likely to be important characters. They would probably have very different reactions to Naruto's new appearance. Sasuke might be initially confused or indifferent, while Sakura could be either shocked or find it hilarious.
In this fanfiction, it could be that Naruto is forced to dress as a girl due to a prank or a magic spell gone wrong. As a result, he has to navigate his daily life in Konoha while looking like a girl, which causes all sorts of chaos and interesting interactions with his fellow villagers.
One possibility is that he's trying to prove a point. Maybe there's some discrimination or unfair treatment towards girls in the wizarding world that he wants to highlight. By dressing like a girl, he can put himself in their shoes, so to speak. Another reason could be that he's influenced by a new friendship or relationship. He might have a close female friend who has inspired him to try dressing like a girl, either as a form of bonding or because he admires her style.
Once there was a mother who loved the idea of having a daughter. She had a young son. One day, she decided to dress him up like a girl for a family photo. She put him in a pink frilly dress, tied a big bow in his hair, and even added some cute little shoes. The son was a bit confused at first but went along with it because he loved his mother. When they took the photo, everyone was amused and the mother was very happy with how cute her 'little girl' looked.
Perhaps Kyle's dressing like a girl could be part of a magical or supernatural event in the fanfiction. Maybe he wakes up one day magically transformed into a girl - like appearance. This could lead to all sorts of adventures as he tries to find a way to reverse it, all while dealing with the reactions of his friends and family. And along the way, he might learn some valuable lessons about himself and those around him.
He might start wearing dresses, which could be of various styles like a flowy summer dress or an elegant evening gown. His hair might be styled differently too, perhaps in long curls or a cute ponytail.
One possible reason could be that the mom has always wanted a girl. Maybe she had dreams of dressing up a daughter in cute frilly dresses and bows, and when she had a boy, she couldn't resist the urge to fulfill some of those desires in a way. Another reason might be that she wants to break gender norms. She could be trying to teach her son that clothes don't have a gender and he can be comfortable expressing himself in any way he likes.
One reason could be for comedic effect. In fanfiction, authors often like to play with the characters' usual personas. Naruto is known for being a rambunctious boy, so seeing him in a girl's outfit can create a humorous situation. Another reason might be for a disguise plot. Maybe he needs to infiltrate a place where only girls are allowed, so dressing as a girl is a practical solution.