Often, the sharingan gives Naruto an edge in understanding Fu's motives and powers. For example, he can use the sharingan to copy some of her unique jutsu. Another plot point could be the trust - building between them. Since Naruto has the sharingan, a power not native to him, Fu might be initially suspicious but then they grow to rely on each other.
One popular 'sharingan naruto x fu fanfiction' might be 'Naruto's New Bond with Fu'. In it, Naruto's sharingan abilities (which is an interesting crossover concept as sharingan is from Uchiha in Naruto) interact in unique ways with Fu's powers. It shows how their combined powers can face different challenges in the Naruto universe.
If Naruto had the Sharingan, his battle skills would change. Hinata would be both in awe and a bit worried about this new Naruto. Their relationship could develop through her trying to understand this new power of his. For example, she might offer to help him train to control the Sharingan's abilities, like the genjutsu. During these training sessions, they would grow closer and their relationship would take on a new dimension of mutual understanding and support.
In fanfiction, Naruto could get the Sharingan through a blood - related connection that is revealed later. For example, it could be discovered that he has some distant Uchiha ancestry that gets activated somehow. Maybe a powerful enemy's attack awakens this dormant Uchiha blood in him, and as a result, he develops the Sharingan. It could also be that a powerful sage or a new character uses their own unique powers to bestow the Sharingan upon Naruto for a specific purpose.
In these fanfictions, the idea of Naruto with the Sharingan opens up a whole new world of possibilities for his abilities. Kushina, on the other hand, has her own strong personality and backstory. When you mix these two elements, you get stories that can explore things like Naruto's growth in a different way. For example, how he uses his Sharingan - influenced powers to protect the things Kushina holds dear, like the village. It also allows for unique storylines about family bonds and the power of heritage.
A possible plotline could be that Naruto, with his sharingan, discovers a hidden connection between Yugito's tailed beast and an ancient power. They then embark on a quest to unlock this power to save the shinobi world from a new threat. Another plotline might be that Naruto's sharingan allows him to enter Yugito's mind - scape where she is struggling with her inner tailed beast. He helps her gain control and in the process, they fall in love.
One idea could be a story where Naruto is transported to the world of Kung Fu Panda. He meets Po and they train together. Naruto could learn some of the unique Kung Fu techniques while also teaching Po about his ninja skills like shadow clones.
If Naruto had the Sharingan in fanfiction, it would likely lead to some interesting power - up scenarios. He could combine the power of the Sharingan with his own massive chakra reserves. This might make him an even more formidable opponent. His training would also take a new turn as he'd have to learn to control and master the Sharingan's abilities, like the different levels of the Sharingan and their unique powers.
Naruto might adapt by first trying to understand the basic functions of the Sharingan. He could start with the simple ability to see chakra flow more clearly. Since he has always been perceptive about people's emotions, he could use the Sharingan to read the emotions of his enemies through their chakra, which would help him in battles.
One drawback could be the strain on his body. The Sharingan is a powerful dojutsu, and Naruto's body, which is used to his own chakra system, might not be able to handle it well at first. This could lead to fatigue and over - exertion during battles.