One possible triggering event could be the loss of a dear friend. Just like Sasuke's awakening of the Mangekyou Sharingan was related to the trauma of Itachi's actions. In a fanfiction, Naruto might witness the death of someone like Kakashi, who has been a mentor figure. This intense emotional pain and the sense of loss could be the catalyst for his Mangekyou Sharingan to awaken. It would add a new layer of depth to his character, as he would have to deal with this new power and the grief that came with its awakening.
Perhaps it could be triggered by a threat to the entire village. Naruto has always been the protector of Konoha. If a powerful enemy, stronger than any they've faced before, attacks and nearly destroys the village, the overwhelming fear and determination to save his home could lead to the awakening. He would see the destruction and the people in danger, and his Sharingan could awaken as a means to gain the power necessary to fend off the threat. This would also show his growth as a ninja, from just being a regular fighter to someone with a unique and powerful ability.
The awakening might be related to his connection with the Nine - Tails. In some fanfiction concepts, Naruto's Sharingan could be affected by the chakra of the Nine - Tails. If the Nine - Tails' chakra is somehow manipulated in a way that it merges with Naruto's latent Uchiha blood, it could cause the Mangekyou Sharingan to awaken. This would create an interesting dynamic between Naruto's Uzumaki and Uchiha sides, and he would have to learn to control this new power that is a result of this strange combination.
Perhaps in the fanfiction, Naruto discovers a hidden connection between his Uzumaki heritage and the Sharingan. This newfound knowledge, combined with a great battle against a powerful villain, causes the Mangekyou Sharingan to awaken. It could also involve some sort of ancient prophecy or power that was long forgotten, and Naruto is the key to unlocking it which leads to the awakening of his Mangekyou Sharingan.
It could be a rogue ninja from a forgotten clan who has a vendetta against the Hidden Leaf. This ninja might be seeking to obtain the power of the Mangekyou Sharingan for himself, and sees Naruto as a threat. So, he tries to stop Naruto from fully awakening it and uses all kinds of dark jutsu to attack Naruto and his friends.
In such a fanfiction, one possible plot could be that Naruto acquires the Mangekyou Sharingan through some kind of magical or experimental accident. Maybe a powerful enemy uses a jutsu that backfires and transfers the Sharingan to Naruto. Then Naruto has to learn to control its power while also facing the prejudice from those who fear the Sharingan's abilities.
In many Naruto fanfictions, Itachi is often depicted as an extremely powerful Mangekyou Sharingan user. His original abilities in the canon, like Amaterasu, are further enhanced in fan works. Sasuke is also a common focus. His Mangekyou Sharingan's powers can vary greatly from one fanfiction to another, sometimes with new and unique jutsu created by the authors. Another character could be Madara. Fanfiction writers love to explore the full potential of his Mangekyou Sharingan, often giving him abilities that were only hinted at in the original series.
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.
One possible plot twist could be that Naruto's Sharingan has unique abilities not seen in the regular Uchiha Sharingan. Maybe it can combine with his Sage Mode in unexpected ways, like seeing chakra flows more clearly even in Sage Mode, enhancing his combat skills.
In this fanfiction, perhaps the awakening of the Sharingan gives Naruto an edge in battles that makes the female ninjas admire him even more. The plot might involve Naruto being initially confused by all the attention from the girls, but then gradually coming to terms with it. For example, Sakura could see him in a new light and Hinata might be even more smitten. And this new dynamic could lead to various adventures and challenges as Naruto tries to balance his relationships with his duties as a ninja.
Well, in the 'Naruto awakens the Rinne Sharingan fanfiction', it's possible that Naruto's character arc takes a whole new turn. With the Rinne Sharingan, he might be able to see the chakra flow in a much more detailed and different way. Maybe he could even communicate with the tailed beasts on a deeper level, using the unique abilities of the Rinne Sharingan. This could lead to new forms of cooperation between them and Naruto, which would be really exciting for the story.
One creative plot twist could be a character who was thought to be a normal ninja suddenly reveals they have a Mangekyou Sharingan with a unique power that changes the whole power dynamic in the story. For example, a side character who has been helping the main character all along, but then uses their Mangekyou Sharingan to stop an impending doom that no one else could. Another could be that the Mangekyou Sharingan has the ability to swap the powers of other ninjas, creating chaos and new alliances.
The Eternal Mangekyou Sharingan is a very powerful and significant element in Naruto fanfiction. It represents a high - level evolution of the Sharingan. In fanfictions, it often gives the characters who possess it extraordinary abilities, like enhanced visual powers, the ability to use unique and powerful jutsus.