It could also be a result of a powerful jutsu gone wrong. For instance, a forbidden jutsu that alters the fabric of reality and somehow makes Naruto become his own father within the fanfiction world. In this case, he might have to deal with the new family dynamics and the responsibilities that come with being a father in a very strange and unexpected situation.
Perhaps in the fanfiction, there is a dimension where the laws of genetics and family relations are completely different. Naruto could find himself in this dimension and be recognized as his own father due to some unique property of that world. He would then need to navigate this new identity while still retaining his own Naruto - like qualities and skills.
Well, in such a fanfiction, the Naruto world would be a chaotic mess. Naruto as Kushina's father would mean the timeline of events related to the Uzumaki clan and Konoha would be all jumbled up. His relationship with Sasuke would also be affected. They were rivals because of their different family situations and goals. But with this new family setup, Naruto's motives and Sasuke's perception of him would be very different. And Naruto's status in the village might be completely different too, as his relation to Kushina would give him a different kind of standing in the Uzumaki - related matters in Konoha.
Well, if Naruto is the father of Mikoto in the fanfiction, it could bring a whole new dynamic. Naruto is known for his strong will and his ability to make friends and change people's minds. As Mikoto's father, he might instill in her the same values. Also, considering Naruto's connection to the Nine - Tails, there could be some interesting plot twists. For example, Mikoto might have some sort of special ability related to the Nine - Tails or Naruto could have passed on some of his chakra to her, which would give her an edge in battles.
One possible storyline could be that Naruto is forced into fatherhood due to some sort of political arrangement. For example, a village in need of an alliance might demand that Naruto have a child with a princess from their village. Naruto, being the selfless hero, would accept this for the sake of peace. He would then struggle to adjust to this new role while still having his duties as a ninja. He might initially be clumsy at parenting, but gradually learn and grow into a loving father.
Well, it could be anyone really. It might be some random ninja that Rouge had a relationship with. Or it could be a character created specifically for this fanfiction. Maybe it could even be a character from another village who had a secret liaison with Rouge.
Yes, he can. In fanfiction, the writer has the creative freedom to cross different universes. Naruto could be a father in a Highschool DxD setting perhaps through some sort of interdimensional travel or magical event. Maybe he's brought into the Highschool DxD world and starts a family there. It's all about the wild and creative ideas that fanfiction allows.
In fanfiction, the idea of Naruto being Annabeth's father might start with a portal or time - travel element. For example, Naruto could be sent through a portal to the world of Annabeth. He might save her mother from a great danger, and in the process, they fall in love. Then, Annabeth is born. Another way could be that there is a curse or a prophecy that links their two very different worlds together, and Naruto is fated to be her father.
One possible story could be a crossover where the worlds of Naruto and High School DxD collide. Naruto, perhaps through some magic or time - travel - like event, ends up in the DxD world and has a relationship that results in Issei's birth. Another could be a story where Naruto has some sort of hidden connection to the devils in DxD and his bloodline gets mixed, leading to Issei. There could also be a story where Naruto is reincarnated in the DxD world and starts a new family, with Issei being his son in that new life.
One possible power is the ability to use chakra. Since Naruto is known for his large chakra reserves, Blake could inherit a strong chakra pool. This would allow her to perform powerful jutsus, like maybe a modified version of the Shadow Clone Jutsu that suits her own combat style. Another power could be enhanced speed and strength, which Naruto also has, and Blake could use these in her battles more effectively.
One possible reason could be that Naruto feels abandoned. His father was not around during his childhood, and he had to face a lot of hardships alone. Growing up without a father figure, he might have developed resentment.
Well, one way could be if Naruto has some new, super - powerful jutsu that he's developed. Maybe he's found a way to combine his Sage Mode with his Nine - Tails chakra in a completely new and unexpected way that gives him an edge over Hashirama.