As the Juubi Jinchuuriki in fanfiction, Naruto may face challenges like dealing with the corrupting influence of the Juubi's power. He has always been about friendship and protecting others, but this power could make him more aggressive. Also, there could be political challenges as other villages may see him as a threat and try to undermine him.
In fanfiction, if Naruto becomes the Juubi Jinchuuriki, he would face several challenges. Firstly, there's the physical toll that such a powerful entity inside him could take. He might have to constantly fight to keep his body from being overloaded. Secondly, he would have to deal with the moral implications of having so much power. He has to ensure he doesn't use it for wrong reasons. And thirdly, he would have to deal with those who would want to take the Juubi's power from him, whether it's rogue ninja or power - hungry individuals from other villages.
One possible challenge is controlling the immense power. The Juubi's power is so vast that it could be difficult for Naruto to keep it in check. Another challenge might be how others perceive him. People could fear him and try to isolate him.
In a fanfiction where Naruto becomes the Juubi Jinchuuriki, his appearance might even change. He could have markings or an aura that shows his new status. His role in the shinobi world would be completely redefined. He would no longer be just a powerful ninja but a being on a whole different level. He could use the Juubi's power to heal the land that has been damaged by years of war. And his enemies would have to think twice or even a hundred times before attacking him as his power would be so overwhelming that it could mean instant destruction for those who oppose him.
One challenge could be controlling the power of the Juubi. It's an incredibly powerful and chaotic force. Naruto would have to struggle to keep it in check so that it doesn't overwhelm him and cause him to lose control. If he loses control, he could end up harming his friends and allies instead of protecting them.
One big challenge would be public relations. Sasuke has a dark past, and some villagers might not trust him completely. Also, he's not as naturally warm and approachable as Naruto. He'd have to work on that. Another challenge could be dealing with the paperwork. Sasuke is used to being out in the field, not sitting behind a desk. And he might face opposition from some of the more traditional ninja clans who don't like his new ideas for the village.
One challenge could be cultural differences. Naruto is from a ninja village where things like honor are defined differently compared to Arturia's world of chivalry. Another might be the expectations of their people. Konoha ninjas and Arturia's subjects would have different ideas about how a married couple should behave. Also, they have different power sources. Naruto's chakra and Arturia's magic could cause some misunderstandings when they try to work together in battles or other situations.
If Naruto becomes the Juubi Jinchuuriki in fanfiction, it would be a game - changer. He could potentially change the entire ninja world. His influence would be felt everywhere. With such power, he could even reshape the relationships between the different ninja villages. He might also have to deal with the fact that many would fear his new - found power, and he would have to prove that he's still the same Naruto at heart, just with a whole lot more power to protect those he loves.
Naruto would also have to deal with the physical differences. As a girl, she might not have the same physical strength she had as a boy. This could be a big issue in combat situations, as she would need to adapt her fighting style. Maybe she would have to rely more on agility and strategy rather than brute force.
One challenge would be the secrecy. Naruto is used to being open and honest with his friends, but in ANBU, he has to keep things hidden. Another is the new type of missions. He may not be used to the stealth and assassination - type missions that ANBU often undertakes.
One challenge would be dealing with students who don't respect his authority. Naruto was always a bit of a rebel himself, so he might find it hard to enforce strict rules. Another challenge could be teaching complex ninja techniques to students with different levels of ability.
One challenge could be controlling his newfound power. The Juubi's power is immense and Naruto might struggle to not accidentally cause destruction while time - traveling. For instance, a simple movement or action might have a much larger impact on the timeline due to his increased power.
In this fanfic, Naruto might gain incredible power. He could have enhanced physical abilities like super strength and speed. His ninjutsu might also reach a whole new level, allowing him to perform feats that were previously impossible.