In this fanfiction, the plot could center around Naruto's past as an orphan and how it relates to Sirzechs' own experiences. They could bond over their struggles and use their combined powers to bring peace to both their realms. Naruto could introduce concepts like chakra to the Underworld, while Sirzechs could teach Naruto about the politics and magic of his world. Their brotherly relationship would be a key factor in uniting different factions within both worlds.
In a fanfic where Naruto kills Sirzechs, it could be a very interesting concept. Maybe it's a crossover universe where the power dynamics are completely different. Naruto, with his powerful jutsu, might have a reason like protecting his own world from a perceived threat by Sirzechs. However, it also depends on how the author has set up the story, the rules of the world they've created, and the motives given to Naruto for such a drastic act.
One possible scenario could be that Naruto somehow ends up in the world where Fem Sirzechs exists. Maybe through a strange rift in space - time. They could start as allies, with Naruto's powerful jutsu and Sirzechs' own formidable abilities combining to face a common threat. For example, they might battle against a powerful dark force that threatens both of their worlds. Naruto's positive attitude could also influence Fem Sirzechs in ways that change her perspective on certain things in her world.
Rock Lee with his incredible taijutsu skills could be a part of the peerage. His determination and physical strength would be assets. Neji, before his death, with his Byakugan and combat abilities might have been a suitable addition as well. And Hinata, with her gentle nature yet strong Byakugan - based skills, could also be considered for the peerage.
His abilities might be enhanced by the demonic powers associated with Sirzechs' world. For example, his Rasengan could take on a more demonic form, with added destructive power. Maybe he could also gain the ability to teleport short distances like some demons in Sirzechs' world, which would give him an edge in combat.
He could also feel angry. After all, he has fought for his friends and the village. To be betrayed by someone like Sirzechs would make him want to prove his innocence. He might start training even harder to show that he is not the bad guy Sirzechs is making him out to be. And he would likely try to find evidence to clear his name.
His character might also become more empathetic. As he glares at Sirzechs' power, he could start to understand the responsibilities that come with great power. Through interactions with Sirzechs or observing how Sirzechs uses his power, Naruto might learn to be more understanding of others with great power and the choices they have to make. This could lead to a more well - rounded Naruto who not only has physical strength but also emotional intelligence.
In this fanfiction, it might be that Sirzechs is being manipulated by some dark force. This dark force convinces Sirzechs that Naruto is evil. As a result, Sirzechs betrays Naruto. Naruto then has to not only deal with the betrayal but also figure out how to stop this dark force that is causing so much chaos and misunderstanding.
Perhaps they meet when both are on a quest for a powerful and ancient artifact. This artifact could have the potential to change both of their worlds in significant ways. Along the way, they would face many challenges. Naruto's rasengan and other jutsu would be used to fight off enemies, while Fem Sirzechs could use her strategic mind and her own unique powers to outwit their foes. As they progress, they develop a deep respect for each other.
One possible reason could be a clash of personalities. Naruto is from a world with its own set of values and power systems, and Sirzechs is from a different fictional universe. Maybe Naruto, in the context of the fanfiction, sees Sirzechs' power or attitude as something he dislikes. For example, if Sirzechs has a very different view on leadership compared to Naruto's idea of it, that could cause friction.