One idea could be an OC from a modern world suddenly getting the Sharingan and being thrust into the Naruto universe. They could use their modern knowledge along with the power of the Sharingan in unique ways, like using technology to enhance the Sharingan's 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.
First, you need to create your original character (OC). Decide on their personality, background, and any unique abilities they might have apart from the Sharingan. Then, think about how they will get the Sharingan. Will it be through some kind of accident, a gift, or something else?
Another idea is a crossover with a superhero universe. Imagine a character like Sasuke with his Mangekyou Sharingan powers suddenly in the Marvel or DC universe. He could team up with heroes like Spider - Man or Batman. His Sharingan's ability to copy moves could be really interesting when facing off against super - villains.
One interesting plot idea could be an OC with a Sharingan who transfers to the Highschool Dxd world. They could use their Sharingan abilities to detect the devils' true forms and powers. For example, during a Rating Game, the OC could analyze the opponents' strategies in an instant using the Sharingan's precognitive abilities.
Another plot could involve a crossover between Naruto's world and a character from the Uchiha clan who has the Rinne Sharingan. They could team up to face a common enemy that is threatening both their worlds. Along the way, they would learn from each other's abilities and cultures. For example, Naruto could teach the Uchiha character about the power of friendship and teamwork, while the Uchiha could show Naruto some advanced Sharingan techniques.
One idea could be a story where the Sharingan evolves to an ultimate form that gives Naruto unique powers. For example, he might be able to use it to instantly teleport to any location he has previously visited. This would add a new dimension to his fighting abilities and his ability to save his friends quickly.
One idea could be a story where the protagonist discovers a new and unique power within the Mangekyou Sharingan that has been lost for generations. This power could give them an edge in battles against powerful foes like the Akatsuki. Another plot could revolve around a character who has to overcome the dark side effects of using the Mangekyou Sharingan, such as losing their sight at a faster rate. They could search for a way to counter this while still using the power to protect their village.
One idea could be that Naruto discovers a hidden Uchiha ancestor in his family tree. This could lead to the dormant Sharingan gene awakening in him. He then has to learn to control the Sharingan while still maintaining his own unique ninja abilities. Another plot could be that during a battle with a powerful enemy, Naruto is somehow merged with an Uchiha ninja, and as a result, he gains access to the Sharingan. He then uses it to gain new insights into his opponents' moves and strategies.
A cool plot idea might be a Sharingan warrior from a different dimension coming into the main Naruto universe. This warrior has a unique way of using the Sharingan that no one in the main universe has seen before. They could either become an ally or a formidable enemy, depending on their motives. Their presence could disrupt the existing power balance and force the characters in the Naruto world to adapt and find new ways to combat this new threat or form new alliances with this strange visitor.
Another plot could revolve around a character who accidentally acquires the Rinne Sharingan and has to learn to control it while being hunted by various groups. Some might want to use the power for their own evil purposes, while others fear the unknown capabilities. This character could start as a relatively weak ninja but gradually become stronger as they master the Rinne Sharingan, forming alliances with unexpected characters along the way.