Naruto could become more confident. If the leotard is a symbol of his connection with the Kyuubi, wearing it might make him feel more in control of his power. He might start to take on more leadership roles in battles or in his village.
The Kyuubi itself might develop a different relationship with Naruto. Instead of just being a force within him, it could become more of a mentor figure. Through the leotard, which could be a physical manifestation of their bond, it could teach Naruto new jutsu or ways to use his chakra more effectively.
Other characters in the Naruto world might start to view Naruto differently. If he's constantly wearing this unique leotard related to the Kyuubi, they might see him as even more of a force to be reckoned with. This could lead to both positive and negative reactions. Some might respect him more, while others might become jealous or fearful of his growing power.
Another possible development is that she gains the ability to transform into different forms not just for combat but also for communication. For example, she could take on a more human - like form to better interact with the villagers, which helps to bridge the gap between her and the humans and also shows her adaptability and evolution as a character.
In this fanfiction, Naruto could develop his skills in a new way. Since he is dealing with a banished Fem Kyuubi, he may have to learn different ways to communicate and work with her. This could lead to him becoming more adaptable. The Fem Kyuubi might develop from a vengeful being into one who is more forgiving. She realizes that not all humans are bad through Naruto's kindness, and this changes her view of the world and herself.
The Kyuubi in this fanfiction could be depicted with a more feminine form as well. It could have a large, bushy red tail that trails behind Fem Naruto when she's in the leotard. The eyes of the Kyuubi could glow with a fierce, yet somewhat alluring light.
In this fanfiction, perhaps Naruto's physical abilities are enhanced as the Kyuubi's kit. He might be able to move faster, jump higher, and his strength could be superhuman. Also, his relationship with Sasuke could change. Sasuke might see Naruto as an even greater threat or, on the other hand, an ally he needs to understand better. And Naruto could start to have a different understanding of his own identity and place in the ninja world.
For Naruto, he may gain a new perspective on power. Instead of just seeing the Kyuubi as a source of brute strength, he could start to understand the deeper, more complex nature of the tailed beast. This could lead to a more mature Naruto, one who is not just about fighting but also about protecting through a more nuanced use of power. The male Kyuubi could experience a change in his view of humans. He might see that not all humans are out to control or harm him, especially with Naruto as his'mate'. He could become more empathetic towards the human world and be more willing to cooperate with Naruto's goals.
For Naruto, he could develop more understanding of the darker side of the ninja world through his interactions with Tayuya. Tayuya, on the other hand, might start to see the value of friendship and loyalty like Naruto has. For example, Naruto's unwavering belief in his friends could rub off on Tayuya, making her question her previous solitary and somewhat ruthless ways.
One possible plot development could be Naruto gaining new and extremely powerful abilities. For example, he might be able to use Kyuubi's chakra in more refined ways, like creating unique jutsu that combine his own skills with the raw power of the Kyuubi. This could make him nearly invincible in battles against his enemies. Another aspect could be his relationship with his friends and the village. With the new power, some might fear him while others try to understand and support him. It could also lead to Naruto having to face new and stronger foes who are attracted by his enhanced power.
One idea could be that Naruto discovers a special leotard that has the power of the Kyuubi sealed within it. He then has to learn to control this newfound power while also facing off against enemies who want to steal the leotard for its power.
Anko might develop a softer side through her interactions with Naruto. She has a tough exterior due to her past, but Naruto's unwavering optimism and kindness could start to break down her walls. She could become more open and trusting towards others in general.
In such a fanfiction, perhaps there would be a spiritual journey for Naruto. As he's dying while sealing the Kyuubi, he could have visions of his past, his friends, and his dreams. He might see the faces of Iruka - sensei who first recognized him, or Hinata's loving looks. This could give him the strength to complete the sealing process. After his death, the village could start to remember and celebrate his life in different ways. Statues could be erected in his honor, and his story could be told to every new ninja trainee as a legend of self - sacrifice.