Typically, he would have the Sharingan in his eyes. So, instead of his normal blue eyes, one or both of his eyes would have the characteristic red with the tomoe pattern of the Sharingan. It gives him a more menacing look, which is quite a contrast to his usual friendly appearance.
Naruto's fighting style would change significantly. He would no longer rely solely on his brute strength and Rasengan - based attacks. The Sharingan would allow him to see the flow of chakra more clearly, so he could target his opponents' weak points more precisely. He could also use genjutsu, which he has little experience with before. Maybe he would combine his shadow clones with the Sharingan's abilities, for example, having clones with Sharingan - enhanced vision to scout the area better during a battle.
I really like 'Obito's New Path'. In this fanfiction, Obito gets a second chance in a different reality. His Sharingan abilities are explored in unique ways, like how he uses it to understand the true nature of the ninja world. The story also has great character development for Obito and other Naruto characters.
If Naruto has Obito's eyes in fanfiction, his abilities would be enhanced in several ways. The Sharingan's ability to see chakra flow clearly would allow Naruto to better analyze his opponents' moves and weaknesses. With Kamui, he could teleport himself or objects, which would be a huge advantage in battles. He might also be able to use some of the more advanced Sharingan - related genjutsu, adding another layer to his combat skills.
He could change in terms of his relationships too. His friends might be both in awe and a bit wary of this new power he has. Naruto himself might struggle with the newfound power, as it's not his natural ability. He might become more introverted as he tries to master it privately, not wanting to accidentally harm his friends with this new, potentially dangerous power.
Typically, he might gain some Hollow - like features. His eyes could change, perhaps becoming more like a Hollow's with a yellowish glow or a different shape. His hair might also take on a wilder look, almost as if it has a life of its own, similar to how a Hollow's reiatsu can make their hair seem to move unnaturally.
Obito's influence would likely make Naruto more aware of the darker side of the ninja world. Naruto is usually very optimistic, but with Obito's guidance, he would see the hardships and betrayals that can happen. For example, Naruto might become more cautious in his trust of others.
In fanfiction, the naruto kyuubi suit can change his appearance quite a bit. His hair could become more wild and take on a reddish tint, like it's being influenced by the Kyuubi's chakra. His eyes might glow a different color, perhaps a deep red. Also, the suit itself could be form - fitting and have a pattern that resembles the Kyuubi's fur. This makes Naruto look more intimidating and shows his connection to the powerful nine - tailed fox.
Often, Naruto's appearance may change to incorporate some of Kurama's features. He might have red - tinged hair or his eyes could take on a more fox - like appearance, like slitted pupils or a red glow.
In the 'Naruto Mata Sharingan' fanfiction, it can also change the training and development of characters. A character with this combination of powers would need to train in both Naruto - style chakra control and Sharingan - related skills. This would open up new training methods and challenges. They might also discover new jutsus that are a combination of the two power sources. This would not only change the individual characters but also the overall balance of power in the Naruto universe, as new and unexpected abilities emerge from this unique combination.
Naruto might become more reserved. Since Obito has a more brooding personality, Naruto could pick up on some of that. His once - bright and exuberant nature might be tempered.