There could be a story arc where Naruto uses his new appearance as a girl to his advantage in espionage or undercover missions. This would bring in elements of mystery and intrigue. His interactions with other villages' ninja would also be different, and he could use this to gain information or form new alliances in a way that he couldn't as a male Naruto.
One possible plot development could be that Naruto's new look causes confusion among his friends. They might start to question if he's still the same Naruto they know. Another is that enemies could be either more afraid or more eager to fight him, thinking he has some of Madara's power.
Fem Naruto might develop a more motherly or nurturing side. Kushina was known for her strong personality and also her love for her family. Fem Naruto could inherit some of these traits and become more protective of her friends, almost like a mother figure to them. This would be a significant change from the original Naruto's character in some aspects.
It could be just for the fun of it. Writers often like to play with the established characters and create unique scenarios. In this case, seeing strong Naruto in a girl - like form can lead to humorous situations, like when his friends first see him and their shocked reactions. Also, it can open up new plotlines, such as Naruto having to disguise himself as a girl for a mission and having to navigate the situation while still being his strong self.
One possible plot development could be that Naruto is mistaken for Madara by some of the older characters who knew Madara. This could lead to some interesting confrontations and misunderstandings.
Perhaps there could be a story where a love interest of Kirito's doesn't recognize him because he looks like a girl. This could create a lot of emotional turmoil and misunderstandings. The love interest might start to develop feelings for 'female - Kirito' without realizing it's actually the person they already knew. It could be a really angsty and interesting storyline.
One possible plot development is that they team up to take on a common enemy that neither of their villages could handle alone. This enemy could be a powerful rogue ninja or a group with a dangerous new jutsu.
One possible plot development could be Naruto getting into more intense battles with stronger opponents. Since Kenpachi is always seeking strong battles, Naruto may start to do the same. This could lead to him exploring new areas to find worthy foes.
Often, when Naruto is made to look like a girl in fanfiction, his clothing might change to something more feminine. He could be dressed in a simple kimono - perhaps a light - colored one with floral patterns. This new appearance might cause different reactions from the other characters. For example, Sasuke might be initially shocked but then gradually see that it's still the same strong - willed Naruto underneath. And Naruto's strength could be shown in a different light. Instead of brute physical force, it could be more about his mental tenacity and strategic thinking, which are not affected by his new appearance.
One possible reason could be in the realm of artistic interpretation in the fanfiction. The author might want to explore a different aesthetic or a unique plot where Naruto has some physical or behavioral traits similar to Orochimaru for shock value or to create a new kind of character dynamic.
One possible reason is their physical appearance. They might have some similar facial features or hair color that could give the impression. Another reason could be their skills. If in fanfiction, Tobirama's skills are exaggerated and Naruto has similar - looking skills, it could lead to this idea. Also, their status in the ninja world as important figures might contribute.