One idea could be a story where Sasuke, with his Sharingan, discovers a new power related to the Rinnegan that was hidden within Naruto all along. Maybe Naruto has some dormant Sage of Six Paths energy that when combined with Sasuke's powers, they can unlock a new level of strength to fight a powerful, unknown enemy.
Another theme is the bond between Naruto and Sasuke. Since the Sharingan can be a connection between them in some fanfictions, it's often used to explore their relationship. It could be about how they understand each other better through the Sharingan, or how it helps them to forgive and trust each other again. For instance, in some stories, the Sharingan reveals hidden emotions and memories that strengthen their bond.
One possible fanfiction could be where Naruto, through some strange and unforeseen circumstances, like a powerful jutsu gone wrong that somehow transfers Sasuke's Sharingan to him. Naruto then uses this new - found power in ways that make Sasuke respect him more. For example, Naruto might use the Sharingan's ability to predict movements to counter an enemy's attack and save Sasuke, leading to a stronger bond between them.
A cool plot could be that a new villain emerges who has the ability to nullify the powers of the Sharingan and Rinnegan. Naruto and Sasuke have to find a way to overcome this without relying solely on their eye powers. They might discover ancient techniques that their predecessors used before the existence of these eye powers.
A really interesting one is 'Sasuke's New Path with the Sharingan'. Here, Sasuke discovers a new and unexpected use of his Sharingan. The story also focuses on his relationship with Naruto as they both grow and change. It's a more character - driven story that really makes you think about their bond.
A fanfic could explore a scenario where Sasuke decides to teach Naruto some basic Sharingan techniques. Despite Naruto not having the Sharingan, Sasuke believes that Naruto's ability to learn quickly and his unique chakra could allow him to adapt some of the Sharingan's skills. This would strengthen their friendship as they train together and Naruto starts to understand Sasuke's power on a deeper level.
In such a fanfiction, an interesting plot point could be that Naruto's chakra starts to mix with the Sharingan's power in unexpected ways. This could lead to the creation of a new type of Sharingan or a new power altogether. Maybe Naruto's Uzumaki bloodline affects the Sharingan in a way that no one expected. Also, the power struggle within Naruto as he tries to balance his own values with the new power of the Sharingan could be a great source of internal conflict and an interesting plot point.
The fanfic could be centered around Sasuke's best friends, Naruto and Sakura, and how they interact with Sasuke's Sharingan. For instance, Naruto might be curious about the Sharingan's abilities and constantly ask Sasuke to show him new tricks. Sakura, being a medical ninja, could study the Sharingan's effects on Sasuke's body to ensure he doesn't overuse it and harm himself.
In a fanfic like this, Sasuke's Sharingan could be the key to unlocking a hidden power within his best friends. Maybe his Sharingan has a special connection to Naruto's Nine - Tails chakra. As they fight side by side, Sasuke uses his Sharingan to guide Naruto in controlling the Nine - Tails better. Sakura, on the other hand, could learn new medical jutsu inspired by the insights from Sasuke's Sharingan, deepening their bond as they all grow stronger together.
They could go on a journey to find a way to heal any negative effects of the Sharingan on Sasuke. Naruto would be by his side every step of the way, providing emotional support. As they travel, they face various challenges, and Sasuke uses his Sharingan to analyze the situation while Naruto uses his brute strength. Their combined efforts make them an unbeatable team.