It could change the relationships Naruto has with other characters. For example, his friends might be shocked at first but then become protective of his daughter. His enemies could see her as a new target or a way to get to Naruto.
One possible storyline could be that Naruto discovers he has a daughter in a very unexpected way. Maybe she was hidden away by an enemy for some dark purpose. As Naruto uncovers the truth, he has to deal with his own guilt for not knowing about her and also protect her from those who would still do her harm.
The mother could also be a completely new character created specifically for this fanfiction. She might be from a different realm or have some special powers. And her relationship with Percy could be a complex one, filled with secrets and misunderstandings that led to the situation of having a secret daughter.
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.
Perhaps the plot could involve Percy's daughter discovering her true identity on her own. She might start to notice strange things about herself or her father's behavior. For example, she could find some old letters or artifacts that hint at her origin. And as she digs deeper, she gets closer to the truth, which also brings her closer to the dangerous world her father has been shielding her from.
It could be Hinata. In the original series, Hinata has a deep affection for Naruto. In a fanfiction, it would be a natural progression for her to be his secret fiance. Maybe they got engaged secretly to avoid some political unrest in the village.
It might also be Gaara. Their initial encounters were filled with tension, but as the story could be twisted in fanfiction, that could develop into a different kind of relationship. Gaara's own journey of self - discovery and Naruto's influence on him could be a basis for a romantic relationship in fanfic.
Well, it could be a fanfiction where Naruto discovers he has the Mokuton ability in a very unexpected way. Maybe he gets it through some ancient power transfer or a connection to a long - lost clan. And this new power of Mokuton could lead him to face new enemies or form new alliances. It might also explore how his friends react to this new side of him.
It could be that Naruto is secretly training a new and powerful jutsu that he doesn't want anyone to know about yet. Maybe he's afraid that if his enemies find out, they'll try to stop him before he perfects it.
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.