If Naruto becomes the Juubi in fanfiction, he would likely gain an incredible amount of power. He might be able to reshape the ninja world. His physical abilities would be off the charts, with strength, speed, and durability far beyond what he had before. His chakra reserves would be limitless, allowing him to perform extremely powerful jutsus without tiring easily. Also, his new form could potentially change the balance of power among the ninja villages, making Konoha the most dominant force. And he could use this power to protect his friends and the entire ninja world from any threat.
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.
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.
In this 'naruto the juubi crossover mass harem fanfiction', the plot might revolve around Naruto being thrust into a situation where the Juubi's energy somehow creates a harem around him. It could start with Naruto's battle against the Juubi. After some kind of encounter with the Juubi's power, female characters from various places start to flock to him. They could be attracted by his new - found power related to the Juubi or some other mysterious connection. Naruto would then be in a position where he has to balance his ninja duties, understanding the Juubi, and dealing with his new - found relationships.
Well, it could be about Juubi Naruto being transferred to the Highschool DxD world. Maybe he'd use his unique ninja skills to stand out among the devils and angels there. And with the harem aspect, he might attract the attention of various female characters from both universes.
Definitely Hinata. Since she has feelings for Naruto in the original series, she could be a part of the harem. Sakura might also be there as she is an important female character. From the Juubi - related side, maybe a female form of one of the tailed beasts. Also, Tenten could be included as she is a strong female ninja. And perhaps a mysterious female character who has a special connection to the Juubi's power.
Well, if Naruto becomes the Juubi in a time - travel fanfiction, one possibility is that he could use his new - found power to change the course of history. Maybe he'd prevent some of the great tragedies that happened in the Naruto world. He could also use the Juubi's power to gain a deeper understanding of the chakra system and teach others about it, leading to a new era of ninja development.
His character would develop in a more complex way. He'd have to grapple with the new power and the responsibility that comes with it. He might become more isolated at first as others fear his power. But then he'd learn to use it for good and become more confident in his abilities.
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.
He could fit in by being the new and mysterious student. His different powers and abilities would make him stand out. The girls in the harem would be curious about him.