Perhaps a curse or a powerful magic spell is cast that merges the two worlds. Naruto, Inuyasha and their friends have to find a way to break the spell. In the process, they exchange their skills and knowledge. Naruto teaches the Inuyasha gang about chakra and how to use it, while Inuyasha shows Naruto some of the secrets of the demon world and how to fight more effectively against demons.
One interesting plot idea could be that Naruto somehow gets transported to the Inuyasha world. He teams up with Inuyasha and they have to face a common enemy, like a powerful demon that is threatening both the ninja world and the feudal Japan world. Naruto's unique jutsu combined with Inuyasha's sword skills would make for some epic battles.
One idea could be a character from the Hanyou world ending up in the Naruto universe and having to adapt to chakra. Maybe they could teach the ninja some unique fighting styles from their world in return. Another idea is a crossover of the two worlds' magic systems, like how Inuyasha's Tessaiga might interact with Naruto's Rasengan.
A cool plot could be that there's a tournament across different anime worlds, and Inuyasha and Naruto are chosen to represent their respective worlds. Along the way, they discover similarities in their pasts, like both having some form of demon - related heritage (Naruto with the Nine - Tails and Inuyasha being a half - demon). They also exchange combat techniques. Naruto teaches Inuyasha how to better use chakra control in his attacks, and Inuyasha shows Naruto some unique sword - fighting skills.
A really unique plot could be a situation where the tailed beasts in Naruto are related to the powerful demons in Inuyasha. For instance, the Nine - Tailed Fox could have a connection to a major demon in Inuyasha's world. This discovery could lead to a journey where Naruto has to travel through the Inuyasha world with Inuyasha and Kagome to find out the truth about this connection and how it can help or harm their respective worlds.
One plot idea could be that Naruto and Inuyasha are somehow transported to a new world where they encounter a group of unique female characters. They have to work together to survive and in the process, a harem situation starts to develop as the girls are attracted to their different qualities. Naruto's determination and Inuyasha's rough - edged charm draw the ladies in.
A possible plot could involve the Hollows from Bleach somehow making their way into the Inuyasha universe. Inuyasha and his friends would have to team up with Ichigo and the Soul Reapers to fight them. This would create a really interesting dynamic as the different fighting styles and powers collide. The Hollows might also target the demons in Inuyasha's world, seeing them as a new source of power or prey.
One idea could be that Inuyasha gets transported to the Ouran High School world. He'd be this wild and rough - around - the - edges character in a posh, refined school setting. Maybe he mistakes the Host Club for some sort of demon - like group at first and tries to fight them. Another plot could involve a character from Ouran getting dragged into Inuyasha's feudal Japan world and having to adapt to the lack of modern conveniences and the presence of demons.
Well, a cool plot for this crossover fanfiction could be that the Pokemon trainers are summoned to the Inuyasha world to help stop a new evil that is related to both the Pokemon world and the Inuyasha world. Maybe a villain has found a way to combine the power of the Shikon Jewel with a powerful Pokemon artifact. The trainers and their Pokemon have to work together with Inuyasha and his friends. Some Pokemon might evolve during the intense battles, and the Inuyasha characters could learn about the concept of evolution in the Pokemon world, which could be a fun aspect to explore.
Well, perhaps in the fanfiction, Naruto's Kitsune Hanyou side starts to emerge during a battle. Hinata is the first to notice the change in him. This could lead to a story where Naruto struggles to control his new powers at first. Hinata, using her Byakugan and her understanding of Naruto, helps him. They might then have to deal with the political implications of Naruto being a Kitsune Hanyou in a world that has some prejudices against such beings. Their love story could develop as they break down these barriers and prove that Naruto's new identity is not a threat but a strength.
Perhaps there could be a common enemy that both Inuyasha and Naruto have to face. A powerful demon or a rogue ninja who has found a way to travel between their worlds. They would have to combine their unique skillsets, like Inuyasha's speed and strength along with Naruto's Rasengan and his ability to inspire others. Their friends would also play important roles, like Sakura helping with medical needs and Kagome providing spiritual support.
One idea could be an Inuyasha and Naruto crossover. Picture Inuyasha in the Hidden Leaf Village, his sword skills and demon powers causing quite a stir among the ninja. Another could be a crossover with Harry Potter. Inuyasha at Hogwarts, trying to figure out magic while also dealing with his own demon - slaying business. Maybe he'd have some interesting interactions with the magical creatures there.