A third concept could be that there is a prophecy in both the Inuyasha world and the Young Justice universe that foretells the coming together of certain heroes. Inuyasha and the Young Justice team are brought together to fulfill this prophecy. They have to overcome their differences in culture and fighting styles to defeat an ancient evil that is trying to destroy all of existence. It would be an epic battle with lots of action and drama.
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.
One idea could be a crossover where Ben Tennyson ends up in the Young Justice universe. He could team up with the young heroes to fight a common enemy. Maybe a group of villains from both universes join forces, and Ben uses his Omnitrix to transform into different aliens to help in the battles.
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.
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.
Another fanfiction could be set in a post - apocalyptic world where the power of the Demon Fox Lord has been misused in Naruto's world, and it has some sort of ripple effect on Inuyasha's world. Inuyasha and Naruto, both having a connection to powerful spiritual forces, must find a way to restore balance. They could start off as enemies, misunderstanding each other's motives, but gradually come to realize they need to work together.
One idea could be that the Shinju's power somehow connects the Naruto universe and the Justice League's universe. Maybe the Shinju's energy creates a rift, and Naruto characters end up in the Justice League's world. They could team up to fight a common enemy that is attracted by the strange energy of the Shinju. For example, a powerful demon from Naruto's world could be drawn to the new universe and the Justice League, with their high - tech and superpowers, join forces with Naruto and his friends who have ninja skills and chakra abilities.
Another possibility is a post - Endgame fanfiction. After the events of Endgame, the Avengers discover a new threat that has ties to the Justice League's world. Maybe a powerful villain from the DC universe has somehow been awakened by the events in the Marvel universe. So they have to reach out to the Justice League for help and together they figure out a way to stop this new threat.
One idea could be a crossover where Goku is accidentally transported to the Justice League's universe. He might initially be seen as a threat due to his power but then they realize he's a good - hearted fighter. They could team up to fight a common enemy like Darkseid who has somehow acquired the Dragon Balls and is using them for his evil plans.
One idea could be that Iron Man's technology gets mixed up with Justice League's alien tech. Maybe he creates a new suit using some of the Kryptonian crystal technology he discovers while working with Superman. This new suit gives him powers similar to Superman for a short time, but it also has some unexpected glitches that lead to humorous or dangerous situations.
Well, it could be that the writer is a big Inuyasha fan and wanted to incorporate that character into the Young Justice universe for a unique crossover. Maybe they thought Inuyasha's abilities, like his swordsmanship and demon powers, would add an interesting dynamic to the Young Justice story that Kagome's skills might not.
One idea could be that a character from the Naruto universe with the Rinnegan somehow gets transported to the DC universe where the Justice League exists. They could initially be seen as a threat, but then prove their worth by helping the League against a common enemy. For example, using the Rinnegan's abilities like the Six Paths powers to combat a powerful villain like Darkseid.