In some fanfictions, Naruto might get the Mangekyo Sharingan due to a connection with Sasuke. For example, Sasuke could be in a life - threatening situation and Naruto, in his desperation to save him, somehow inherits the Mangekyo Sharingan. This would lead to a whole new dynamic in their relationship, with Naruto now having a power that was once exclusive to Sasuke's clan.
One possible plotline could be Naruto unlocking the Mangekyo Sharingan through some strange and unforeseen means, perhaps a powerful jutsu backfires and gives him this new power. Then he has to struggle with controlling it while his friends are both amazed and a bit worried about this new development in him.
Another concept is the character development. The presence of the Eternal Mangekyo Sharingan often brings a deeper level of conflict and growth for the characters. They might have to struggle with the power it bestows, such as the risk of going blind or the moral implications of using its more sinister abilities.
One interesting plot idea could be a character from the Naruto world obtaining the Mangekyo Sharingan through some strange and unforeseen event. For example, Naruto himself could be exposed to a powerful Uchiha - related jutsu that accidentally gives him the Mangekyo Sharingan. This would completely change his power dynamic and how he approaches battles. He could then have to learn how to control this new power while still maintaining his own ninja way.
Another plot could revolve around a character who has the Mangekyo Sharingan but is trying to hide it from both their allies and enemies. They fear the power it holds and the attention it might draw. As the story progresses, they are forced to use it in a crucial battle, and their friends then have to deal with the revelation and the potential danger it brings to the group.
Sasuke Uchiha is often a central character. Since he already has the Sharingan in the original series, in fanfiction with the Eternal Mangekyo Sharingan, he can be further developed. His journey to master this new level of power and how it affects his relationships, especially with Naruto, can be a major focus.
One possible plotline could be the main character having a unique form of the Sharingan that gives them powers beyond what is normal in the Naruto universe, like the ability to time - travel. This could lead to them changing the course of major events in the Naruto story.
One possible plotline could be the main character with the Rinne Sharingan finding themselves in a world where they are surrounded by multiple characters from Naruto in a harem - like situation. They might have to navigate complex relationships while also dealing with the power of the Rinne Sharingan and the threats that come with it.
It could be an original character. Maybe a young ninja from a small, forgotten clan who discovers they have the Mangekyo Sharingan. This character would have to learn about their power, its limits, and how to use it in a world full of powerful shinobi.
Naruto would likely become more introspective. The Mangekyo Sharingan often comes with a lot of emotional baggage in the Naruto universe. So, Naruto might start to question his own identity more, especially since this power is from a clan he has no blood relation to. He could also become more cautious as he learns about the potential dangers of misusing the Mangekyo Sharingan.
One possible plotline could be Naruto suddenly gaining the Sharingan through some mysterious jutsu accident. With the Sharingan, he could quickly learn new techniques and have enhanced perception. Combined with the Kyuubi's power, he might become an almost unbeatable force. For example, he could use the Sharingan to better control the Kyuubi's chakra flow, making his attacks more precise and powerful.
Another plotline could involve Naruto using the Obito's Sharingan to unlock some hidden secrets about the Uchiha clan. He might discover something that even the remaining Uchiha members didn't know. With his unique ability to mix his Uzumaki chakra with the Sharingan's power, he could unearth ancient Uchiha techniques or prophecies. This could put him in a position where he has to protect this new knowledge from falling into the wrong hands, like those of the Akatsuki or other enemy ninja groups.