One idea is that an enemy targets Kakashi's Sharingan and Naruto has to protect it. Along the way, Naruto learns more about the Sharingan's capabilities and how to use it against the enemy. This would be a great opportunity for Naruto to grow as a ninja and for their friendship to deepen.
Maybe in the fanfiction, Kakashi transfers a part of his Sharingan's power to Naruto temporarily. Naruto then uses this power to enter a special dimension where he has to face his own inner demons. With the help of the Sharingan - like power, he overcomes them and returns stronger, ready to face new challenges in the real world.
A possible plot could be that Naruto is given a temporary Sharingan by an ancient Uchiha spirit. With this Sharingan, he starts to see the world in a different way, and he realizes that there are hidden threats in the ninja world that only the Sharingan can detect. He then embarks on a journey to find out more about these threats and how to stop them. Another plot could be that Naruto meets an Uchiha survivor who teaches him how to use the Sharingan in a way that no one else has thought of. This new way of using the Sharingan could help Naruto in his fight against the Akatsuki. And there could also be a plot where Naruto's Sharingan evolves in a unique way because of his Uzumaki heritage.
One idea could be a story where Naruto somehow gains the Golden Sharingan. He could use its unique powers to see through genjutsu more easily and also have enhanced perception in battle. For example, he might be able to predict his opponents' moves better. Another plot could involve Naruto using the Golden Sharingan to unlock a new form of his Rasengan, perhaps one with the ability to disrupt an enemy's chakra flow on a deeper level. Or, it could be a story where Naruto has to team up with a character who has knowledge of the Sharingan to fully understand and control the Golden Sharingan's powers.
One idea could be a story where the main character, who has the Eternal Sharingan, has to face a new and powerful enemy that can manipulate time. With the power of the Eternal Sharingan, the character has to find a way to break the enemy's time - based attacks and defenses. Another plot could revolve around a character with the Eternal Sharingan trying to uncover long - lost secrets of the Uchiha clan that are hidden deep within the Sharingan's powers. Maybe there are ancient jutsu or prophecies that only the Eternal Sharingan can unlock.
One idea could be a character from RWBY obtaining the Sharingan and using its abilities in combat. For example, Ruby could get the Sharingan and combine its precognitive abilities with her own speed, making her an even more formidable fighter.
One idea could be that Hatake Kakashi somehow transfers his Sharingan to Naruto in a dangerous mission. This would give Naruto new abilities and a whole new set of challenges to face. He'd have to learn to control the Sharingan quickly while also dealing with the enemies who might target him specifically for it.
One idea could be that the character with the Sharingan is banished due to false accusations of using its power for evil. He then has to journey alone, facing challenges and learning to control his power in new ways. Maybe he meets a group of outcasts who he befriends and together they fight against the unjust system that banished him.
One idea could be exploring a different origin for the Mangekyou Sharingan. For example, what if it was related to an ancient Uchiha pact with a hidden spirit? Another could be a story where a non - Uchiha character somehow gains the ability to use the Mangekyou Sharingan and has to deal with the consequences. Or perhaps a fanfiction where the Mangekyou Sharingan has additional powers that are not shown in the original Naruto series, like the ability to time - travel.
A really interesting plot for 'kakashi and naruto family fanfiction' could be that Kakashi accidentally stumbles upon a secret power within Naruto's family that has been dormant for generations. He then helps them unlock and control this power. Along the way, they form a stronger bond as a family. And as Kakashi is involved, he also rediscovers some of his own values and beliefs through this process.
One plot idea could be that the female Naruto has a special training session with Kakashi. During this, she discovers a new jutsu that Kakashi has been secretly working on. He decides to teach it to her because he sees her potential. This new jutsu then becomes crucial in a future battle against a powerful enemy.
One interesting plot idea could be Kakashi getting transported into a different Naruto timeline where all the villains have joined forces. He'd have to use his Sharingan and vast combat experience to survive and find a way to stop them. Another could be Naruto and Kakashi swapping bodies for a while. This would lead to some comical situations as Naruto tries to act like Kakashi and vice versa. Also, a crossover where Kakashi is sent to a parallel universe where Naruto doesn't exist, and he has to train a new group of ninja in the ways of Konoha.