Their relationship could be developed further through mutual understanding. For example, Naruto could learn more about Kurama's past and the reasons for his anger and hostility in the beginning. This would make Naruto more empathetic towards Kurama, and Kurama in turn could start to trust Naruto even more.
Another way is if Naruto starts to teach Kurama about the positive aspects of human nature, like friendship and loyalty. This could make Kurama more empathetic towards humans and strengthen their bond. Kurama, in turn, could share his ancient wisdom with Naruto, making Naruto a wiser ninja.
One way is through shared experiences. For example, they could go on a journey together outside the village. During this journey, they face challenges like bad weather, lack of food, and dangerous animals. As they overcome these challenges together, their bond grows stronger. Also, Naruto could introduce Kurama to his friends, and Kurama could learn to interact with humans in a more friendly way. This would show that their relationship is not just about being sealed together but about true friendship.
Their relationship could develop further if they face a really tough challenge together, like a super - strong enemy. Through that struggle, they would understand each other better. For example, if they have to fight an enemy that can manipulate time, they would need to trust each other completely and that would strengthen their bond.
To develop their relationship in fanfiction, one approach could be to give the female Kurama a backstory that makes her more relatable to Naruto. Say she was once a normal fox in the forest before being transformed into a powerful being. Naruto, with his kind heart, would be sympathetic to her situation. They could also have moments of cultural exchange. Naruto could teach her about human traditions, and she could share with him the ancient knowledge of the fox spirits. This exchange of ideas and experiences would help build a strong relationship between them. Moreover, having them face internal conflicts together, like Naruto's struggle with his own power and the female Kurama's identity crisis, would also strengthen their bond as they support each other through these tough times.
They could start training together more often. Since Tsunade is a great medical ninja and has a lot of combat experience, she could teach Sakura some advanced medical and combat techniques. This shared learning experience would strengthen their bond.
One way is through joint training sessions. Sarutobi Sensei could push Naruto to his limits and in the process, they would learn more about each other's strengths and weaknesses. Also, they could be put in a situation where they have to rely on each other completely, like being trapped in a dangerous genjutsu. Sarutobi Sensei could then use his wisdom to guide Naruto out, strengthening their relationship. Another aspect could be Sarutobi Sensei introducing Naruto to important figures from his past, which would give Naruto more context about his sensei and bring them closer.
Their relationship can be developed by showing them facing challenges together. For instance, when Naruto has to make tough decisions as Hokage, Hinata can be there to support him morally. And when Hinata has to deal with her family's expectations, Naruto can encourage her to follow her own path. This mutual support can deepen their connection.
Their relationship can be developed through shared adventures. For example, going on a mission to rescue hostages. Naruto can teach Mitsuki how to better understand the emotions of the hostages and use that in battle strategy. This would deepen their bond as teacher - student and friends.
One unique way to develop their relationship is through art. In the fanfiction, Naruto could have the ability to draw out Kurama's chakra in a new form using his own creativity. This would be a new way of interacting that combines Naruto's love for art and his connection to Kurama. As they explore this new form of chakra manipulation together, their bond deepens.
A really unique way to develop their relationship is to have them swap abilities for a short period. Naruto gets some of Kurama's fox - like abilities and Kurama gets some of Naruto's human abilities. This forces them to understand each other's perspectives in a whole new way. They have to learn how to use these new abilities and in the process, they become closer. Another aspect could be that they are both transported to a parallel dimension where they are the only ones who know each other. They have to rely solely on each other to survive and find a way back home, which would greatly enhance their relationship.