Her experiences in the ninja world would play a huge role in her development. If she witnesses a great tragedy, it could make her more empathetic or more determined to prevent future disasters. On the other hand, if she experiences great success early on, she might have to deal with the pressure of maintaining that success and not becoming overconfident.
It could be an original character created just for the fanfiction. Maybe a mysterious ninja woman who crossed paths with Kakashi during a mission and they had a brief but intense relationship.
Depending on the plot of the fanfiction, there could be a love interest for Pain's daughter. This character could be from a different clan or village. Their relationship could be a key aspect of the story, with all the challenges that come from their different backgrounds and the situation of the ninja world.
She could be really energetic, just like Naruto. Maybe she has his blond hair and blue eyes too. And from Fuu, she might inherit some kind of unique chakra or special ability that makes her stand out among other ninja.
The daughter could also inspire a new generation. Young ninjas in the village might look up to her, especially if she has unique skills. This could lead to a change in the way ninjas are trained or how they view loyalty and family in the context of being a ninja.
One interesting story could be about Pain's daughter growing up in the Hidden Rain Village. She might have unique powers that set her apart from others in the village. Maybe she tries to understand her father's actions and has a moral struggle within herself.
A storyline might involve the OC daughter being trained by Itachi in the ways of the ninja, and she becomes a prodigy. As she grows, she might face challenges in the form of rival ninja who are jealous of her skills or her connection to Itachi. Also, there could be a story where she tries to reunite Itachi with Sasuke in a more peaceful way than in the original Naruto story.
Well, perhaps the story could be about the daughter discovering her own unique abilities that are different from Kakashi's. This could lead to some interesting father - daughter bonding moments as he tries to help her develop those powers. Also, there could be a plotline where the daughter gets involved in a mission that is related to Kakashi's past, and they have to work together to solve it.
She might inherit Naruto's strong will and determination. Since Naruto is known for his never - give - up attitude, their daughter could have that same tenacity. She might also have Yugito's unique kekkei genkai, which could make her a very powerful ninja in the fanfiction world. And perhaps she'd have Naruto's blond hair with some of Yugito's physical features.
She could be a very determined person. Growing up with Naruto as her father, she would have heard all about his struggles and achievements. So, she would likely strive to be as great as him. Maybe she'd be a bit of a rebel too, since she's not growing up in the traditional Konoha environment.