Well, in some fanfictions, the story might start with Naruto being sent to a different dimension which is the world of High School DxD. There, he might meet a female character and fall in love. Due to his powerful genetics, their child could be Issei. Or maybe there's a prophecy in the DxD world that a powerful outsider like Naruto will father a special child, which turns out to be Issei. It could also be that Naruto's chakra or some unique ability he has gets passed on to Issei in a way that makes their father - son relationship important to the story's plot, like Issei having some Naruto - like powers that he has to master.
A possible fanfiction story could involve Naruto, who has already achieved peace in his own world, decides to explore other universes. He stumbles upon the High School DxD universe. There, he befriends some of the key characters. Eventually, he meets a character who he has deep feelings for. Their union results in Issei's birth. In another scenario, Naruto could be captured by some evil force in the DxD world. To escape, he makes a deal that involves him having a child with a certain character, and that child is Issei. There could also be a story where Naruto's spirit is transferred into a new body in the DxD world and he starts a new life, with Issei being his son as part of this new beginning.
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.
Issei might inherit Naruto's chakra. This would give him the ability to perform ninja techniques like the Shadow Clone Jutsu. He could create multiple clones of himself to confuse enemies or help with tasks. Also, he could potentially inherit Naruto's ability to sense negative emotions, which would be useful in detecting threats.
In some fanfictions, it's possible for Naruto to be Issei's father. Fanfiction often takes creative liberties and can create some really out - there family relationships. However, in the original Naruto and High School DxD (where Issei is from) canons, there's no such connection.
Well, it could start with Naruto being a bit clueless about fatherhood at first. He might try to teach Issei some of his ninja skills, like how to throw a kunai or use chakra. As time goes on, they could bond over protecting their home from threats. Naruto's never - give - up attitude would also influence Issei, making him more determined in his own pursuits.
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.
One possible character development could be Naruto's role as an older, more established figure. Instead of being the young, energetic hero, he would be more of a father figure. His attitude towards the village and his comrades might be more paternal. He might be more focused on protecting Kushina and guiding her, rather than going on adventures as in the original story.
Since it's a fanfiction, his traits could be anything. He might be a powerful ninja with amazing jutsu skills.
Yes, there might be such fanfictions out there. Fanfiction writers often come up with creative crossovers like this. You can try searching on popular fanfiction websites using relevant keywords like 'Naruto Issei older brother' to find them.
Well, it would be really interesting. Naruto has his own set of values like perseverance and friendship. If he were Issei's father, he might instill those values in Issei. Maybe Issei would grow up with a different kind of power, not just the Sacred Gear from his original story but also some ninja techniques from Naruto. And Naruto would probably be very protective of Issei, teaching him how to fight and face challenges in a more ninja - like way.
One big challenge would be cultural differences. Naruto is from a ninja - based culture where things like honor and clan loyalty are important. Wendy is from a world of magic and guilds. Naruto would have to understand and adapt to Wendy's world's values. Also, he might face opposition from some in Wendy's world who don't trust an outsider.
In fanfiction, anything is possible. However, in the original Naruto series, Kakashi is not Naruto's father. But in the realm of fan - created stories, an author could come up with an interesting plot where Kakashi is Naruto's biological father, perhaps by creating some elaborate backstories and twists to make it seem plausible.