A possible plot is that baby Naruto with his fox ears and tail is found by a group of friendly animals in the forest. They take him in and protect him from the villagers who might be scared of his appearance. As he grows up among the animals, he learns their ways of survival and also starts to discover his own ninja - like abilities that are related to his fox features.
One idea could be that Naruto discovers his fox ears and tail have special powers. For example, the ears can detect danger from afar, like an enhanced sense of hearing. The tail could be used for balance during his high - speed ninja moves, making him even more formidable in combat.
One possible plot could be that Naruto discovers a new jutsu or is under a curse that causes him to grow fox ears and a tail. This new form might make his friends initially confused or even a bit scared. But as the story progresses, he learns to control this new part of himself and uses it to his advantage in battles, like having enhanced senses from the ears and better balance with the tail.
One possible reason could be a strange side - effect of his connection with the Nine - Tails. Since he has the Nine - Tails' chakra within him, in the fanfiction world, this chakra might start to physically manifest in the form of fox ears and a tail during his time in Wave. Maybe the unique environment or a specific event in Wave triggered this abnormal transformation.
Maybe in the fanfiction, Naruto's fox ears and tail are a result of a new jutsu gone wrong. This new jutsu was supposed to give him some sort of enhanced connection to the Nine - Tailed Fox's power, but instead it physically manifested these features. As a result, he has to figure out how to reverse it while also dealing with the reactions of his friends and the villagers. His friends might be initially shocked but then try to help him, while the villagers could be more fearful and start to treat him differently.
In a fanfiction, Female Naruto with fox ears and tail might have a special connection to the Nine - Tailed Fox spirit. The fox ears and tail could be a sign of a deeper bond that she has with the tailed beast. This could lead to new jutsu or abilities that are related to both her femininity and the fox - like nature. For example, she could create illusions that are fox - themed or use her tail as a weapon in a more graceful way than normal attacks.
One idea could be that Naruto has to constantly hide his ears and tail from the villagers at first. This could add an extra layer of secrecy and danger to his early life, as if he's discovered, he might face more severe persecution than in the original story. Another plot idea is that his fox features give him unique abilities, like enhanced senses, which he has to learn to control.
One origin could be a curse placed on Naruto. In the Naruto universe, there are many powerful curses. This curse could be related to the nine - tailed fox's history or some ancient feud. It might be that a long - forgotten clan or entity has put this curse on Naruto as a form of revenge or to serve their own dark purposes. Or it could be a natural evolution of Naruto's connection to the nine - tailed fox as he reaches a new level of power, but his body isn't fully able to handle it yet, so it manifests in these physical changes.
One idea could be that Naruto's new fox features give him enhanced senses. He could use his improved hearing to detect hidden enemies or his sharpened sense of smell to track down missing ninjas. For example, in a mission to rescue a kidnapped villager, his new abilities help him find the secret lair of the enemy much faster than his teammates.
The fanfiction could be set in an alternate universe where having fox ears and tail is normal for some ninjas. Female Naruto would be part of a group that is trained specifically to use their fox - like features in combat. There could be rival groups with different animal - like traits, and she has to fight for the honor of her fox - clan.
Another idea is that the fox ears and tail are a sign of a prophecy. In the fanfic, Naruto is the only one with these features and they mark him as the one who will bring balance to the ninja world. This could involve him having to face off against dark forces that want to prevent the prophecy from being fulfilled. He'd have to learn to master his new features to succeed.