One idea could be Naruto being transported to the Young Justice universe during the Invasion arc. He could use his unique jutsu skills like the Rasengan to fight off the invaders. Maybe he teams up with the Young Justice team and teaches them some of his ninja techniques.
A possible fanfiction could revolve around Naruto's chakra being mistaken for some sort of new power source in the Young Justice Invasion plot. The team might be suspicious of him at first, but as they see him use his powers to protect innocents, they start to trust him. He could also have some interesting interactions with the magic - using characters in Young Justice, comparing and contrasting his own ninja abilities with their magic.
Naruto could fit in by being a powerful and unpredictable ally. His skills would give the Young Justice team an edge in combat.
A great plot for Young Justice Invasion fanfiction might be to have the team deal with internal conflicts during the invasion. Maybe there are trust issues among some members because of secrets that come to light. For example, if a member was unknowingly related to one of the invaders. This would create drama and force the team to work through their issues while also fighting the external threat. Also, you could explore how the invasion affects the public perception of the young heroes. Are they seen as saviors or are people scared of them bringing more danger?
Perhaps a story where a character from the Naruto universe, who has a connection to Amaterasu, travels to the Young Justice world. There, they meet a character who has a similar power but in a different form. They exchange knowledge about their powers and together develop a new technique that combines the elements of both their abilities. This new power could then be used to save both worlds from a common threat.
One idea could be that Naruto, as the son of Black Mask, has to struggle with his father's evil reputation while trying to prove himself in the Young Justice world. He might use his ninja skills in unique ways within the context of the Young Justice team's missions.
One idea could be a crossover where a character from Young Justice gains the Rinnegan somehow. Maybe through a strange experiment gone wrong that links dimensions. They then have to figure out how to control its powers while still being part of their team in Young Justice. It could lead to some interesting power - up moments and new story arcs.
One idea could be a crossover where Naruto is somehow transported to the Young Justice universe and teams up with the heroes there, and then they encounter Wonder Woman. Maybe Naruto's unique jutsu skills can be used in a joint mission with the Young Justice team's powers and Wonder Woman's abilities.
In this type of fanfiction, magic could play a role in character development. For Naruto, experiencing a different type of power system like magic in the Young Justice world could make him question his own ninja way. He might start to adapt some of the magic concepts into his own fighting style. And for the Young Justice characters, learning about Naruto's 'magic' (chakra) could open their eyes to new ways of thinking about power and how to use it more effectively.
A more complex plot could be that there is a prophecy in both universes that foretells of a combined force from both Naruto's world and the Young Justice world being the only thing that can stop an upcoming great evil. This would lead to a series of events where characters from both sides have to learn to trust and work together. Naruto could bring his friends from Konoha, and together with the Young Justice team, they would train and strategize to face this ultimate threat.
One idea could be that Naruto is somehow transported to the Young Justice universe. He then has to learn how to work with the team while also dealing with villains he's never faced before. Another plot could be that a villain uses some sort of magic or technology to merge the two worlds, forcing Naruto and the Young Justice members to cooperate to separate them again.
One idea could be to have Inuyasha end up in the Young Justice universe through some sort of magical portal mishap. He could initially be seen as a threat due to his demon nature and his sword, Tessaiga. But then the Young Justice team realizes he's more of a lost soul and they try to help him get back home while also dealing with villains who want to use Inuyasha's power for their own gain.