He may face opposition from some in the village who think that learning Kamui is too dangerous or that it goes against some ninja traditions. This could lead to internal political or social pressure on Naruto, making it difficult for him to focus on his training.
One challenge could be controlling the space - time aspect of Kamui. It's a very complex jutsu, and Naruto, who is used to more straightforward chakra - based attacks, might struggle to understand the intricacies of warping space and time.
In many fanfictions, Naruto might initially discover Kamui through an encounter with Obito or Kakashi. Maybe during a battle where he witnesses the power of Kamui first - hand, and his inquisitive nature leads him to start exploring how to learn it.
One challenge could be the complexity of chakra control required for Particle Style. Naruto has always had a bit of a struggle with precise chakra control.
Another challenge is adapting his fighting style. Naruto's existing fighting style is based on his ninja training and the use of chakra. Ultra Instinct is a completely different concept. He has to figure out how to integrate the new power into his attacks and movements without losing his own identity as a ninja. For instance, he can't just abandon his signature Rasengan, but needs to find a way to use it in conjunction with Ultra Instinct abilities.
Well, for Naruto in this fanfiction, a major challenge would be dealing with the recoil of Raikiri. Since it's a powerful jutsu, it likely has a significant recoil effect on the user. Naruto would need to learn how to manage that so he doesn't get hurt every time he uses it. Also, in the world of fanfiction, there could be other ninja who don't want Naruto to learn Raikiri. They might try to sabotage his training, which would be an external challenge he has to face. And let's not forget that Naruto has his own unique fighting style. He would need to find a way to integrate Raikiri into his existing style without losing his edge in combat.
Naruto using Kamui could change the power dynamics in the Naruto universe in the fanfiction. His battles would become more unpredictable. For instance, against strong opponents like Madara or Kaguya, Kamui could be used in creative ways. He could use it to send parts of their attacks to another dimension, or quickly dodge attacks and counter - attack from unexpected angles. It also might make his allies view him differently, as this new power is something very different from his normal ninjutsu.
In some fanfictions, Naruto might acquire the ability to use Kamui through a special encounter. Maybe he meets an ancient sage who imparts this power to him, seeing Naruto's potential and his need for an edge in battles against powerful foes.
One challenge Naruto might face is the difference in chakra usage. Shunpo seems to require a more refined and quick chakra control compared to his regular jutsu. Also, the physical aspect of it, the sudden and rapid movements, could be tough for him to master at first. He's used to more straightforward combat movements, so the agility needed for Shunpo could be a hurdle.
One challenge could be the physical strain. The Harashin technique might require a different kind of chakra control and physical movement than what Naruto is used to. For example, it could demand more precise and rapid movements, which might be difficult for Naruto at first.
One challenge could be the complexity of the technique itself. Hiraishin is a very advanced ninjutsu, and Naruto might struggle to understand the chakra control required for it.
One challenge could be controlling the natural energy. Since senjutsu involves harnessing natural energy, Naruto might find it difficult to balance it with his own chakra. It's like trying to mix two very different substances without causing an explosion.