Well, in a Young Justice fanfiction, the concept of Naruto being immortal could be integrated in various ways. One way could be through some sort of magical or scientific experiment gone wrong that gives him immortality. Maybe it's a meta - human experiment in the Young Justice universe that accidentally gives Naruto the same powers as Vandal Savage, including immortality. Another possibility is that it could be a result of a powerful jutsu he uses that has unforeseen consequences and makes him immortal.
The integration might involve Naruto having to deal with the moral implications of being immortal in the Young Justice world. He would be an outsider already, being from the Naruto universe, and immortality would set him even further apart. He might have to decide whether to use his immortality for good, like protecting the young heroes in Young Justice, or if it could lead him to be more self - centered. After all, in the Naruto series, he values life highly, so this new state of being would be a huge adjustment.
Perhaps the writers of the fanfiction could link Naruto's immortality to the Lazarus Pits in the Young Justice universe. There could be a connection where the energy or magic in the pits somehow interacts with Naruto's chakra, creating an immortality effect. This would tie in the two different universes in a really interesting way. Naruto could then have to navigate the politics and power struggles that surround the Lazarus Pits, all while trying to find a way back to his own universe if that's his goal.
In a fanfiction scenario, a Young Justice character with fire - based powers could meet a Naruto character who has seen Amaterasu. They would compare their powers. The Naruto character could explain how Amaterasu is more than just fire, it has a spiritual and chakra - based component. The Young Justice character could then try to incorporate some of those concepts into their own power use, leading to a new and stronger form of their fire ability.
One way could be by having Inuyasha be from a different dimension that somehow gets connected to the Young Justice world. Maybe a magical portal opens up and he stumbles through, bringing his own set of problems and abilities with him.
Another possibility is that he could be a part of a multi - dimensional or time - travel plot. Maybe he gets pulled into the Young Justice universe due to some interdimensional rift. His presence could then create a whole new set of storylines, like the team having to deal with the villains that follow him through the rift, or him having to adjust to the different rules and politics of the Young Justice world.
It could also be a character - based integration. A new character inspired by Dark Naruto could be introduced into the RWBY fanfiction. This character might have similar traits such as a thirst for power and a bit of an anti - hero complex. They could interact with the existing RWBY characters, causing conflict and also growth among them.
Susano Naruto in a Young Justice fanfic might also have a cultural impact. Naruto's world has a distinct Japanese - inspired culture, and when combined with Young Justice, which has its own set of cultural elements, it can create a really unique blend. The author could use this to explore themes of acceptance, adaptation, and the clash of different ways of life. For example, how would the heroes of Young Justice react to a power like Susano, which is so different from what they're used to?
Perhaps the lemons are a form of currency in the demon realm. Naruto, in his interactions with the demon king, has to trade lemons for information or help. This could lead to comical situations as Naruto tries to gather enough lemons, and also serious moments when the demon king demands more lemons than Naruto can easily obtain.
One way to integrate it is to have a mad scientist - type character introduce the nanites into Naruto's body. Maybe this character is an outcast from a hidden village who has been secretly researching nanotechnology. He sees Naruto as a perfect test subject and implants the nanites without Naruto's full knowledge at first.
Well, one way is through a training arc. Imagine Naruto's training takes him to a secluded place where an old master lives. The master has a unique training method that involves wearing a Yukata while performing certain ninja techniques. Naruto would have to adapt to the new clothing style while still maintaining his ninja abilities. Also, Naruto could be involved in a rescue mission where the kidnapped person is held in a place where Yukata are an important part of the environment. He might have to disguise himself in a Yukata to blend in and save the day.
Naruto would be a bit of a wild card at first. His brash and head - strong nature might clash with some of the more reserved members of the Young Justice team, like Aqualad. But his determination and loyalty would also be something that the team could quickly come to respect. He would probably befriend Superboy quickly as they both have a bit of an outsider feel.
In some fanfictions, Wally is often portrayed as a bit of an outcast due to his immortality. He feels different from his friends and teammates. His personality might change too. He could become more reserved as he witnesses the passage of time around him. But at the same time, he still has that underlying heroism that makes him a great character.