One interesting concept could be the exploration of a character who once had the Sharingan but then lost it. Maybe the fanfiction delves into how they adapt to life without this powerful ability. For example, they might have to rely more on their other skills like taijutsu or ninjutsu in new and creative ways.
Perhaps it involves the idea of an abandoned Sharingan having some sort of unforeseen consequence. It could be that the Sharingan, even when abandoned, still has a connection to the character's chakra system and causes some sort of imbalance or strange phenomena that the story focuses on.
One interesting concept could be unique Sharingan abilities not seen in the original Naruto series. For example, a Sharingan that can not only predict movements but also manipulate time on a small scale.
One interesting concept could be a character having a blue Sharingan as a unique mutation. It might give them abilities different from the traditional red Sharingan in Naruto. For example, they could have enhanced precognition abilities, being able to see a few seconds further into the future in combat situations. This could make them a formidable opponent or a great ally.
One interesting concept could be a character from another universe getting the Sharingan. For example, a character from a modern - day setting suddenly having the power of the Sharingan. It would create a whole new dynamic as they learn to use it in a world without chakra.
One interesting concept could be the exploration of new jutsu combinations using the Rinne Sharingan. For example, creating unique space - time ninjutsu that surpasses what we've seen in the original series. Another might be delving into the backstory of how the Rinne Sharingan came to be in a particular fanfiction's universe, perhaps it was the result of a long - forgotten experiment.
Well, one interesting concept could be the unique ways the Sharingan is used. Maybe the fanfic explores new jutsus or abilities related to it. For example, the author might create a situation where the Sharingan can not only copy moves but also enhance them in unexpected ways.
One interesting concept could be exploring the reasons behind the abandonment of the Rinnegan in the fanfiction. Maybe it's due to some unforeseen consequences or a character's choice that goes against the typical use of the Rinnegan in the Naruto universe.
One interesting concept is the combination of powers. In fanfiction, often the Mangekyou Sharingan and Rinnegan abilities are merged in unique ways. For example, a character might be able to use Susanoo with the added space - time manipulation of the Rinnegan. Another concept is the backstories created for how characters obtain these powerful eyes. It could be through some long - lost family heritage or a strange encounter with a powerful entity. Also, the exploration of the psychological effects of having these eyes is fascinating. Characters may struggle with the newfound power and the moral implications that come with it.
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.
In this fanfic, perhaps there is a concept of the Sharingan evolving in ways that are completely different from what we know. It could be that the Sharingan has the ability to absorb not just jutsu, but also the life force of opponents, which would create a whole new dynamic in battles and power struggles within the Naruto universe.
Well, in some Sharingan Crossover Fanfiction, a crossover with the Star Wars universe is really cool. The Sharingan could be seen as a sort of Jedi - like power. A character with it might be able to sense the Force in a different way or use their Sharingan - enhanced perception to be a better pilot. Also, crossovers with the Lord of the Rings world can be fascinating. The Sharingan could help in detecting the true nature of the Ring - wraiths or give an edge in battles against orcs.