He probably gains the ability to control the chakra of the Kyuubi more freely. This could mean enhanced strength, speed, and reflexes. He might also be able to use some of the Kyuubi's unique jutsu like the Tailed Beast Ball. His healing factor could be improved as well, allowing him to recover from injuries faster.
Well, his friends might initially be shocked. But Naruto, being Naruto, would probably use his new power to protect them more fiercely. His relationship with Sasuke could become even more complex. Sasuke might see Naruto as a greater threat or a new source of power to rival. For Sakura, she'd be worried about Naruto's well - being and how this new form affects him. And his other friends like Shikamaru would start to strategize around Naruto's new abilities, changing the dynamic of their teamwork.
Well, if Naruto becomes the Kyuubi in the fanfiction, he would likely have an overwhelming amount of power. He might be able to defeat his enemies with ease. But he would also face the struggle of controlling such a powerful and wild force inside him. Maybe his friends would be both in awe and a bit scared of him at first.
One possible scenario in this fanfiction could be that Naruto's transformation into a fox gives him new abilities related to the Kyuubi's powers. He might be able to communicate with the Fem Kyuubi on a deeper level, leading to an interesting dynamic between them. For example, they could team up to protect the Hidden Leaf Village in a more efficient way, using their combined fox - like skills.
In some fanfictions, if Naruto becomes the Kyuubi, he might gain ultimate power. He could have the Kyuubi's full strength and abilities, like its massive chakra reserves. This could make him nearly invincible in battles. He might also change in appearance, perhaps having some Kyuubi - like features. For example, his eyes could turn red like the Kyuubi's, and he may grow claws or fangs. His personality could also be affected, becoming more ferocious and wild at times, but still having Naruto's underlying kindness.
One potential plot could be Naruto struggling to control his new mini Kyuubi form. He might accidentally cause some chaos in the village while trying to figure out how to use his powers.
In such a fanfiction, perhaps Naruto could gain the full power of the Kyuubi and use it in unique ways. He might develop new jutsu that combine his own skills with the Kyuubi's chakra. For example, he could create a super - powerful Rasengan infused with Kyuubi's chakra. And he may face new and more powerful enemies as a result of this new power. Also, his relationships with his friends and allies could be affected, as they might be in awe or a bit scared of his new - found strength.
There could be a storyline where Naruto's mini Kyuubi form attracts the attention of other villages. Some might want to capture him to study his new form, while others might see him as a threat to the balance of power. Naruto then has to deal with the political implications of his transformation. He might have to prove that he is still the same Naruto who wants peace, just with a new power that he can use for the greater good.
If Naruto becomes the Kyuubi in the multiverse fanfiction, the story could explore how the world views him. The Hidden Villages might see him as a threat and try to either contain or eliminate him. On the other hand, some might see him as a new form of hope. He could also encounter different versions of his enemies in the multiverse. For instance, a more powerful Orochimaru or a different form of Madara. This would force Naruto to constantly adapt and grow in his new state.
It can be considered popular. Fanfiction is all about exploring different ideas, and this concept is quite out - of - the - box. Some fans are attracted to it because it gives a whole new perspective on Naruto's character and his relationship with the powerful Kyuubi. However, it may not be as mainstream as some other common fanfiction themes like Naruto getting new powers or having different romantic relationships with other characters from the series, but it still has a significant following.