I'd recommend 'The Older Brother Naruto'. It shows Naruto as an older brother who has to balance his ninja duties with looking after his younger siblings and teaching them valuable life lessons.
There are quite a few. One popular one is 'Brother's Bond' where Naruto takes on the role of an older brother with great responsibility and care.
The older brother in the fanfiction might be a character with a tragic past. For example, he could have been experimented on by Orochimaru and gained some strange powers as a result. And he returns to the village later to protect Naruto from the threats that are coming towards him.
One idea could be that Naruto, with his strong sense of justice and loyalty, helps Rias in the supernatural politics of her world. He might use his ninja skills to protect her and her peerage from other devils or threats. For example, when facing a powerful rival devil clan, Naruto's shadow clone jutsu could create a diversion while Rias plans a strategic attack.
Yes, there might be such fanfictions out there. The idea of crossing over two very different anime universes like Naruto and High School DxD (where Issei is from) and creating a family - like bond between the characters is an interesting concept that fanfiction writers might explore.
Perhaps in this fanfiction, Naruto has to keep his identity a secret from Minato. He could be from an alternate future where things went wrong, and he's there to make sure Minato becomes Hokage and prevents certain disasters. So he has to subtly guide Minato without revealing who he really is.
In a fanfiction where Naruto is Madara's older brother, it could completely change the Naruto universe's dynamics. For example, Naruto's ideals of peace and friendship might have influenced Madara at a young age, preventing him from going down the dark path he did in the original story. Naruto could have taught Madara about the power of bonds, which was something Madara seemed to have lost sight of later in his life. This would lead to a different series of events, perhaps even averting the many wars that took place in the Naruto world.
If Naruto was the older brother of Kushina, it would rewrite a lot of the backstory. For one, Naruto might be the one to introduce Kushina to Minato. He could see Minato's potential and think he would be a good match for his sister. Also, Naruto's skills and abilities could have a different origin. Maybe he learned some things from Kushina or their family that were unique. This would change his fight scenes and how he approaches challenges in the fanfiction. He might also have a different relationship with the Uzumaki clan as a whole, having more of a family - based influence within it.
No. Naruto and Laxus are from two completely different anime universes, Naruto and Fairy Tail respectively. While fanfiction can play around with all sorts of wild ideas, making Naruto Laxus' older brother is not a mainstream or even a common fanfiction concept. It would require a lot of creative world - building to make such a relationship seem plausible. For example, the writer would have to explain how Naruto, with his ninja skills and chakra system, could exist in the world of magic like Fairy Tail and have a family - like connection with Laxus. But as of now, this is not a typical fanfiction scenario.
Yes, there are likely some fanfictions with this concept. Fanfiction writers often explore unique relationships and alternate storylines. They might create a scenario where Naruto is Sasuke's older brother to develop different character dynamics, explore new plotlines, and add their own creative twists to the Naruto universe.
There could be. Fanfiction writers like to explore different 'what - if' scenarios. Since Naruto and Kushina have a strong connection in the original series, some writers might be intrigued by the idea of reversing their relationship in a fictional context. But it goes against the established lore of the main Naruto storyline.
Well, in this fanfiction idea, Naruto being Sona's older brother could bring a whole new dynamic. Maybe Naruto's protective nature would extend to Sona. He could teach her some of his ninja skills and values like never giving up. It could also create interesting interactions with the other characters in their respective universes. For example, how would the devils in Sona's world react to Naruto's presence? And how would Naruto handle the political aspects of Sona's world which are quite different from his own ninja village politics.