It's not an extremely common theme. While the Naruto fanfiction world is vast and diverse, the idea of the female Kyuubi giving birth to Naruto is quite out - of - the - box. Most fanfictions tend to focus on more traditional relationships like Naruto's growth, his friendships, or his romances. However, there are always some creative and unique fanfictions that explore such unusual concepts, but they are a niche within the larger fanfiction community.
Another possibility is that the father could be a completely new character introduced in the fanfiction. This new character could be from a far - off land and bring some new elements to the story, like different ninja techniques or a new perspective on the ninja world that influences the upbringing of the baby.
Perhaps the fanfiction focuses on how the baby changes the relationships in Naruto's life. Her relationship with Sasuke could be affected, whether they are friends or something more. The baby could also bring new unity among the ninja villages as everyone comes together to protect the new life. And the story could explore how female Naruto passes on her ninja values to her child from a very young age.
It could be a special chakra boost. Since Kyuubi has a vast amount of chakra, it might gift Naruto with an extra dose of chakra that is different from what he already has. This could help Naruto in a difficult battle or in achieving a new jutsu.
It would be a very strange and unique take. It might involve reimagining the origin of Naruto's power. Maybe in this fanfiction, Naruto's connection to the Kyuubi is not just as a jinchuriki but as a son. It could also explore how the other characters in the Naruto world would react to such a situation. Would they be shocked? How would it change Naruto's place in the village?
Well, in some 'Naruto gives birth fanfiction', Naruto may be in an alternate universe where gender roles are different. For example, he could be part of a tribe where men are the ones who give birth. And in this story, his pregnancy journey might involve him learning about new powers that come with the pregnancy, powers that are crucial for the future of the village. There might also be a story where Naruto's birth - giving is a prophecy - fulfilling event, and the whole ninja world is waiting for the birth of this special child with bated breath.
In many fanfictions, this scenario is quite popular. It often delves into the new family dynamics. For example, how Naruto adjusts to being a father while still handling his duties as a ninja. Hinata's motherly role might be explored, like how she passes on the Hyuga traditions to their child.
One possible plot could be that Sakura has a difficult birth. Naruto is by her side, worried sick. Their friends from the village are also there, waiting anxiously. Maybe there are some complications during the birth, and Sakura has to draw on her inner strength as a kunoichi. And in the end, she gives birth to a healthy baby, which brings great joy to the whole village.
I'm not sure specifically if there are age - appropriate ones with this exact concept. However, in the world of fanfiction, there are often different versions. Some authors might take this idea and turn it into a story about Naruto taking on a nurturing role similar to giving birth in terms of emotional investment in new characters or new generations in the Naruto world. It could be a story about growth and new beginnings.
It could be an original character created by the fanfiction author. This character might be a descendant of the original Kyuubi, but with a female form and her own distinct personality.