I'm not sure of specific fanfics on this topic off - hand. But you can check out popular Naruto fanfic websites like Fanfiction.net or Archive of Our Own. Just search for 'Naruto releases Kurama' on their search bars and you should find some interesting ones.
It could be about Naruto finally letting go of Kurama in a very emotional way. Maybe it shows his journey of coming to terms with the loss, and how it changes his relationship with the other villagers.
It could make the plot more focused on Naruto's internal growth as he no longer has Kurama's power. He has to rely more on his own skills and the bonds he has formed with his friends.
Well, it could be about a high - tech world where Naruto has a mecha version of Kurama. Maybe the plot involves fighting new and powerful enemies that can only be defeated with the combined strength of Naruto and his mecha Kurama. The fanfic could also explore how Naruto bonds with this mechanical version of Kurama, different from his connection with the original Kurama.
For Naruto, it would be a whole new experience. He'd be constantly trying to communicate with the mecha Kurama, learning its quirks. Shikamaru might be the one thinking about the strategic uses of mecha Kurama in battle. He'd be coming up with plans on how to best utilize it. As for Kurama, he could be in an internal struggle. Part of him would want to stay relevant in Naruto's battles, while another part would be curious about this new mechanical version of himself and how it could help Naruto in the long run.
Perhaps Kurama has some hidden ability that allows it to manipulate matter at a fundamental level. Using this ability, it could assemble atoms and molecules to construct a new body for Naruto. This process might be tied to the Kekkei Genkai in the fanfic, where the unique genetic trait plays a role in how the body is formed and stabilized.
Well, in some fanfic concepts, Kurama might release Naruto's potential by sharing its own chakra in a more direct and unrestricted way. Maybe it could be like a full-on infusion of Kurama's power, which then unlocks hidden abilities within Naruto that were previously dormant due to Naruto's own self - imposed mental blocks or lack of proper training to handle such power.
Well, in some fanfics, the story might start with Naruto getting a premonition or some kind of sign that Kurama is suffering under the seal. So, he decides to free Kurama. He then embarks on a journey to find a way to break the seal. Along the way, he meets various characters from the Naruto universe who either help or hinder his progress. Once he finally frees Kurama, they team up to face a greater threat to the ninja world that neither could have faced alone.
Kurama can improve Naruto in fanfic through emotional support. Since they have a bond, Kurama can offer advice and motivation to Naruto. It could be like when Naruto is feeling down or facing a difficult decision, Kurama's words of wisdom can give him the confidence to keep going. This aspect can add depth to Naruto's character development in the fanfic.
Well, it's hard to say who the 'best' is as it depends on personal taste. But some popular authors in the Naruto fanfic community often write great Kurama - Naruto related stories. One author to check out might be 'KitsuneWrites'. Their stories usually have really in - depth characterizations of both Kurama and Naruto.