A great fanfiction concept could be set in an alternate universe where Naruto was born with an even stronger bond to Kurama. This connection allows them to communicate telepathically from a very young age and they train together secretly, leading to Naruto being much more powerful early on in his ninja career. For example, they could develop new jutsus that are a fusion of Naruto's human skills and Kurama's chakra powers. This would change the whole dynamic of how Naruto interacts with his friends, enemies, and the village, as he has to keep this secret power a secret from everyone, including his sensei.
A fanfiction idea might be that Kurama gets sick, which is a very unusual situation. Naruto has to find a way to heal him. He travels to different parts of the ninja world, seeking ancient remedies and knowledge. Along the way, he meets various characters who either help or hinder his quest. This could also lead to some character development for Naruto as he realizes how much Kurama means to him not just as a power source but as a friend.
In a fanfiction, imagine a scenario where Naruto loses control of Kurama during a battle, and Gaara is the only one who can calm him down. Gaara uses his own experiences with his tailed beast to reach out to Naruto and Kurama. This could lead to a deeper understanding between the three characters and a strengthening of their bonds.
One idea could be that Kurama is trapped in a special jail within Naruto's mind. Maybe it's a result of some dark magic or a side effect of a new jutsu Naruto attempts. In the fanfiction, Naruto could be desperately trying to find a way to free Kurama while also dealing with the internal chaos that Kurama's imprisonment causes within him.
In the fanfiction, there could be a situation where an enemy attacks the beach area where female Naruto and her friends are having a swimsuit party. Female Naruto, in her swimsuit, quickly springs into action. Kurama's power surges through her, and she uses her ninja skills combined with the unique situation of being in beachwear. For example, she might use her swimsuit's fabric as a distraction or a binding tool against the enemy.
One idea could be that Fem Naruto enters a beach volleyball tournament on the Hidden Sand's beach while wearing a Kurama - themed swimsuit. Her unique look attracts a lot of attention and she has to deal with both admiration and jealousy from other competitors.
In some fanfictions, Kurama can take a human form and interact with Naruto in a more 'human' way. For instance, they could go shopping together in the Hidden Leaf Village.
One interesting idea could be the unique bond between Naruto and Kurama evolving into a more spiritual or emotional'mate' - like connection. This might involve them sharing deeper thoughts and powers in a way that was not explored in the original series.
Maybe the female Kurama was once a human who was transformed into a Kurama due to a powerful curse. In the fanfiction, Naruto could help her break the curse. This would create a deep emotional bond between them as they go through the process of understanding her past and finding a way to reverse the transformation.
One plot could be that the female Naruto is the only one who can calm Kurama during his rages. This gives her a special role in the village. She has to balance her normal ninja training with the responsibility of keeping Kurama in check. It could lead to some interesting situations where she has to use her wits and newfound bond with Kurama to save the village from threats.
One idea could be Naruto and Kurama going on a journey to discover Kurama's past before being sealed. Another could be them facing a new enemy together that only their combined strength as 'brothers' can defeat. Maybe a story where they have to switch places, with Naruto being in Kurama's mind -scape and Kurama having to live in Naruto's world for a while.
In such fanfiction, one interesting idea could be Naruto and Kurama sharing deeper emotional bonds. For example, Kurama might be able to directly influence Naruto's emotions in a more positive way, like giving him instant courage in tough battles. Another idea could be that they can communicate telepathically even more clearly, sharing battle strategies that no one else can understand. And sometimes, they might have the ability to combine their powers in new and unique ways that are not shown in the original series.