The entire ninja world's view of good and evil would be challenged. Naruto was always on the side of good, but as Lucifer, he represents a different set of values. This could cause a moral crisis among the ninja. Young ninja who looked up to Naruto would be confused. The shinobi code might need to be re - evaluated. Also, the spiritual balance in the world, which was maintained by the natural chakra and the various jutsu, would be thrown off. Naruto's new Lucifer - like powers, which could be based on dark and unknown energy, would disrupt the existing energy flow and could potentially lead to disasters such as natural catastrophes or the awakening of ancient evils that were once sealed away.
One way could be through some sort of dark magic or a powerful curse. Maybe Naruto is tricked into performing a ritual that binds him to Lucifer's essence. Another possibility is that in a strange alternate dimension, Naruto's chakra is corrupted and mutates him into a being similar to Lucifer.
If Percy Jackson were to become Lucifer in fanfiction, it could lead to some really interesting storylines. He could use his new Lucifer - like status to rebel against the gods in a different way than he did as Percy. His view of the world would change drastically. For example, he might no longer see the Olympian gods as the ultimate authority. Instead, he could try to create his own order or chaos, depending on how the author interprets the Lucifer character.
Power and its consequences are also a big theme. Naruto has his own set of powers in his universe, and when combined with Lucifer - who is often depicted as extremely powerful - it explores how these powers can be used, misused, or how they change the characters. This can lead to themes of corruption or self - discovery through power.
A fanfiction idea could be that Lucifer from the Highschool DxD universe somehow ends up in the Naruto world. In the Naruto world, he could be seen as a powerful and mysterious figure. He might interact with the ninja clans and shinobi, and his powers could be both feared and respected. He could also have some kind of connection with the tailed beasts or the Sage of Six Paths. The story could revolve around how his presence disrupts or changes the balance of power in the Naruto world.
One possible scenario in this fanfiction could be that Naruto uses his ninja training techniques to help Fem Lucifer develop new skills. Maybe he teaches her stealth, which she can then use in her own realm to gather information more effectively.
I'm not entirely sure if there is a large amount of it, but given the creativity of fanfiction authors, it's highly likely that someone has written a story where Naruto has some sort of connection to Lucifer Morningstar. It could be a really strange or really cool concept, depending on how the author approaches it. You could also check out some Naruto or Lucifer Morningstar fan forums to ask if anyone knows of such fanfiction.
A common theme is the clash of different moralities. Naruto is from a world with a strong sense of right and wrong, while Lucifer has a more complex moral standing. Another theme could be power exchange. Maybe Naruto is offered power by Lucifer in exchange for something.
One plotline might be that the Naruto universe and Lucifer's world collide. Naruto teams up with some of Lucifer's allies (or enemies) to save both worlds from a common threat. For example, a powerful demon from Lucifer's world is trying to invade the ninja world, and Naruto, with his new - found knowledge of Lucifer's powers and the underworld, has to lead the charge to stop it.
One possibility could be that Naruto is drawn to boxing because of its physicality and the determination it requires. He might see it as a new way to test his strength and endurance outside of ninja battles. Maybe he starts training with a local boxing coach who sees his potential and helps him develop his skills.