One possible plot twist could be that Naruto struggles to control the Sharingan at first. Since he's not from the Uchiha clan, the Sharingan's powers might act differently in him. For example, instead of the normal abilities like predicting movements, it might give him visions related to the Uchiha's past traumas. This could lead to Naruto having to deal with not only the power of the Sharingan but also the emotional baggage that comes with it.
His relationship with Sasuke would become really complex. Sasuke, as an Uchiha, might feel a mix of jealousy and concern. Jealousy because Naruto now has a part of what makes the Uchiha special, and concern because he knows the dangers of the Sharingan. They might have more intense battles or training sessions as Sasuke tries to understand how Naruto got the Sharingan and how it's affecting him.
One interesting storyline could be Naruto using the Sharingan to enhance his combat skills in a new and unexpected way. For example, he might combine his Rasengan with Sharingan - powered genjutsu to create a more powerful and deceptive attack.
One possible plot twist could be that Naruto's new Mangekyou Sharingan gives him the ability to access a new form of Sage Mode. Since the Sharingan has unique powers and Sage Mode is Naruto's own power, their combination might create something unexpected. For example, he could use the Sharingan to better target his Sage chakra, making his attacks more precise and powerful.
Well, it changes a lot. For one, Naruto's power level gets a significant boost. Instead of relying solely on his Uzumaki chakra and Sage Mode, he now has the Sharingan's abilities like predicting movements and using genjutsu. This can make battles he's in much more complex and unpredictable.
His powers would change a great deal. Naruto is known for his brute strength and his ability to never give up. The Sharingan would add a whole new layer of finesse to his fighting style. He could use the Sharingan's genjutsu capabilities to trap his enemies in illusions before hitting them with a powerful chakra - infused punch. Also, he could use it to analyze his opponents' weaknesses more quickly, allowing him to adapt his fighting strategy on the fly.
With Sasuke, their relationship would become more complex. Sasuke might be both jealous and intrigued by Naruto having the Mangekyou Sharingan. Jealous because it was always an Uchiha thing, and intrigued because he wonders how Naruto will use it. This could lead to more intense rivalries and also more opportunities for them to understand each other better.
It would change his relationships a lot. His friends like Sakura and Sasuke would be both intrigued and maybe a bit worried. Sasuke, who has his own Sharingan, might see Naruto as more of a rival now. Sakura would be concerned about the risks of the implantation. And his relationship with Kakashi would also shift. Kakashi could help Naruto better understand and control the Sharingan, creating a stronger bond between them as teacher and student.
Maybe it's from a powerful villain. In some fanfictions, this could be a really interesting twist. The DNA of a villain like Orochimaru could give Naruto some of his snake - like abilities or his knowledge of forbidden jutsu. However, Naruto would then have to struggle with the darker instincts that might come with that DNA. Another possibility is that it could be from an ancient and powerful demon. This would bring out a whole new set of challenges and powers for Naruto to deal with.
Maybe Kabuto. He was Orochimaru's right - hand man and had access to a lot of his knowledge and resources. He was also involved in various experiments. Given Naruto's importance in the Naruto world, Kabuto might see the potential in implanting a Byakugan in him. It could be part of a larger scheme to gain an advantage in the ongoing power struggles in the shinobi world.