The sword - Naruto might have the ability to channel his chakra. So it could be used to perform powerful attacks like chakra - infused slashes. Just like how Naruto can use his Rasengan in his normal form, the sword could release a similar type of energy attack when swung with enough force.
Well, it could be really interesting. Maybe Naruto discovers Hinata in a strange situation where she's been cursed or something and she gradually transforms into a sword. Naruto then has to figure out how to reverse it while also using the sword - Hinata in battles against powerful enemies.
It could be due to a magical artifact. Suppose Naruto comes across an ancient and mysterious sword - like artifact. When he touches it or tries to use it, it backfires and instead of him controlling the sword, he is transformed into it. This could lead to a whole new adventure as his friends try to figure out how to reverse the transformation.
I'm not sure if there is such a specific fanfiction. Fanfiction is a vast world with all kinds of creative ideas, but this one seems rather unique. It might be a very niche or even a new and unheard - of concept in the fan - created Naruto stories.
Naruto's personality may not change drastically in terms of his fundamental values like loyalty and the pursuit of his dreams. However, as a girl, he might be more attuned to the social hierarchies among female characters. He could start to notice and react to the cattiness that might exist in some female - only groups in the village. This new awareness could add a layer of complexity to his interactions, but at the same time, he would still be the Naruto who wants to prove himself and protect the village at all costs.
One interesting plot could be Naruto, as a girl, having to deal with the different expectations and treatment from the male characters in the village. For example, they might be more protective or underestimate her skills at first.
Naruto himself is often the focus of transformation in these fanfictions. Since he's the main character, it's interesting to see how different transformations change his abilities and personality.
In Naruto fanfiction, the Kusanagi sword often takes on a significant role. It might be a powerful weapon that Naruto discovers and has to master. For example, it could be hidden in an ancient temple and Naruto, through his adventurous spirit, stumbles upon it. Then he has to learn how to use it in combat against new and powerful enemies.
He could find it in an ancient, hidden temple during one of his missions. Maybe he was exploring a long - forgotten ruin and stumbled upon the sword, completely by accident.