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 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.
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.
Maybe in the fanfiction, the Kyuubi takes on a more human - like form when Fem Naruto is in the leotard. They could form a unique bond and go on adventures together, facing off against other powerful foes in the Naruto universe.
It could be part of a character - building exercise in the fanfiction. By putting Naruto in such an unusual and potentially embarrassing situation, the writer can explore how he reacts, grows, and adapts. For example, he might learn to be more confident in his own skin regardless of what he's wearing.
One common theme could be transformation. The change to the female form and the significance of the leotard as part of that new identity. For example, it might represent a new level of confidence or power.
Yes, in some fanfictions, Naruto is often depicted as the Kyuubi or having a very close connection to it. This can lead to really interesting and unique storylines that deviate from the original plot.
One possible scenario could be that Naruto is forced to wear a female leotard as part of a comical prank by his friends in the fanfiction. Maybe they are playing a truth or dare - like game and this is his dare.
One common plotline is the Kyuubi teaching Naruto new and powerful jutsu. Since the Kyuubi has a vast amount of chakra and knowledge, it could share unique techniques with Naruto that are not part of the regular ninja training. Another plotline could be the Kyuubi's influence on Naruto's relationships. For example, some fanfictions explore how Naruto's connection with the Kyuubi affects how his friends and villagers perceive him. It can also lead to some interesting character development as Naruto has to learn to control the Kyuubi's power without being consumed by it.
In many Naruto fanfictions, Naruto might have developed some new and unique abilities that the Kyuubi has no defense against. This could make the Kyuubi, which is used to being a dominant and feared force, feel vulnerable. For example, if Naruto has the power to nullify the Kyuubi's chakra or to manipulate it in a way that goes against the Kyuubi's will, it would be a cause for fear.