Well, a really interesting plot would be if Kurama got sick or weakened for some reason. Naruto would have to find a way to help him, not just with his chakra, but by searching for rare herbs or asking for help from other tailed beasts. This would test their friendship and show how far Naruto is willing to go to save his friend. Along the way, they could meet new characters or face old enemies who try to take advantage of Kurama's weakened state.
One idea could be that Naruto and Kurama have a day - out in the Hidden Leaf Village. They visit all the places Naruto used to go as a kid, like Ichiraku Ramen, and Kurama makes funny comments about human food. Another could be that they team up to prank the other villagers in a harmless way, just for fun.
One plot idea could be Naruto and Kurama going on a journey outside the Hidden Leaf Village together. They face various challenges like dealing with rogue ninjas or strange beasts. Along the way, they learn more about each other's pasts and grow even closer as friends.
A plot could involve Naruto having to go on a journey within his own mind to save Kurama from some sort of dark influence. During this journey, they discover hidden aspects of each other's personalities. Naruto might find out that Kurama has a soft side that he's never shown before, and Kurama could learn about Naruto's insecurities. This could lead to a stronger bond between them, and when they return to the real world, their combined strength is even greater. And as their relationship deepens, they face challenges from the outside world that test their new - found connection.
Perhaps in the fanfiction, the female Kurama forms a special bond with Naruto where she can transfer some of her unique powers to him in a different way than in the original story. This could lead to Naruto developing new jutsu and facing new enemies that are attracted by this new power. For example, a group of rogue ninjas who want to steal this power-transferring ability.
One idea could be that Yakumo Kurama's unique powers somehow become linked to Naruto's Nine - Tails chakra, creating a new and powerful combination. They could then face a common enemy together that neither could defeat alone.
One idea could be that the Kurama brothers have a secret mission to protect Naruto from an ancient evil that only they know about. They use their unique powers and knowledge to train Naruto in ways that no one else can.
Well, a cool plot in this kind of fanfiction could be that the fusion allows Naruto to enter a new dimension or realm. In this place, he can communicate with past Hokages in a more profound way, getting their wisdom and also learning new ways to use his fused power. Maybe he discovers that the fusion gives him the ability to heal the land that has been damaged by previous battles. This would make him not just a fighter, but also a healer for the ninja world.
One plot idea could be Kurama teaching Naruto some ancient and powerful jutsu that only he knows. Since Kurama has a vast knowledge of chakra and ninja techniques from long ago, he could pass on this knowledge to Naruto in a unique way, like through dreams or during their mental conversations.
One idea could be that the female Kurama has the ability to take on a human form and she and Naruto meet in a secret forest. She initially tries to trick Naruto but ends up falling in love with his pure heart. Another could be that she gets separated from her fox form and has to rely on Naruto to protect her while she regains her strength. And a third idea is that they are both sent on a special mission together by the Hokage, and during the mission, they develop feelings for each other.
An interesting plot could be that there is a prophecy in both worlds that foretells the coming of a being with the combined powers of magic and chakra. Harry Potter and Naruto are both candidates in their respective worlds. Kurama, seeing the potential in their combined strength, decides to guide them both towards fulfilling the prophecy. Along the way, they face many challenges, like learning about each other's powers and cultures. Harry has to adapt to the physical and combat - oriented world of Naruto, while Naruto has to understand the more intellectual and magical aspects of Harry's world. And they have to deal with enemies who don't want the prophecy to be fulfilled.
One plot idea could be Naruto and male Kurama having to team up to face a new and powerful enemy that neither could defeat alone. They start to understand each other's powers and personalities better during the battle. Another could be Kurama teaching Naruto a new and unique form of chakra control that is exclusive to the nine - tailed fox. Or perhaps they go on a journey to discover the origin of Kurama's power and along the way, they form a deeper bond as friends.