One idea could be creating an OC who is a powerful miko from a far - off land. She could have unique powers that even Kagome doesn't possess, like the ability to control the elements in a different way. For example, she can make ice sculptures out of thin air that can be used as weapons against demons.
You could also create an OC who is a human with the knowledge of ancient demon - slaying techniques long forgotten. This OC could team up with Inuyasha and the gang, teaching them new ways to fight demons. She might have found an old scroll in her family's attic that details these lost arts and decides to put them to use in the fight against evil.
An interesting OC mate could be a human with a special connection to the spiritual world. She can see the spirits that Inuyasha sometimes misses. Their story could involve her helping Inuyasha understand the deeper mysteries of the spiritual realm. They might meet when she is being chased by a minor demon and Inuyasha saves her. This event sets off a chain of adventures where they fall in love while uncovering secrets about the world they live in.
One idea could be that the male OC is a powerful mage from a far - off land. He crosses paths with Inuyasha and the gang while on a quest to retrieve a powerful magical artifact that has been lost in Feudal Japan. His magic skills could either complement Inuyasha's fighting style or cause some initial clashes due to differences in their approaches.
One idea could be that the OC is a healer who comes across Bankotsu's gang. Bankotsu is initially skeptical of her but as she heals his wounds, he starts to develop feelings. Another could be the OC is from a rival clan but falls for Bankotsu's strength and charisma, leading to a Romeo - Juliet - style relationship within the Inuyasha universe.
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.
Another interesting concept is that the Jewel of Four Souls has some sort of connection to a powerful and rare Pokémon. The characters from both worlds then have to team up to either protect or destroy this connection, depending on whether it's a threat or a potential boon.
One interesting story could be about a female oc who is a powerful healer. She meets Inuyasha and his group during their travels. She uses her unique healing powers to help them when they are injured in battles against demons. This adds a new dynamic to the group as they now have someone with different skills.
For an Inuyasha male OC fanfiction plot, consider this. The male OC is an artist who can paint things that come to life. He gets caught up in the chaos around the Shikon Jewel when one of his paintings accidentally becomes a powerful demon. Now he has to work with Inuyasha and the others to defeat it. Or he could be a demon slayer who has a personal vendetta against a particular type of demon that is also involved in the Shikon Jewel saga. His presence disrupts the group's dynamics at first, but they soon realize they need his skills. Another idea is that he's a messenger from another dimension who brings news of a greater threat that will affect not only the Inuyasha world but also other dimensions.
One idea could be that Ichigo from 'Bleach' somehow gets transported to the world of 'Inuyasha'. He might meet Inuyasha and they could team up to fight a common enemy, like a powerful demon that has somehow gained the powers of Hollows from 'Bleach'. Their different fighting styles would make for an exciting combination.
One idea could be to cross Inuyasha with a modern detective story. Inuyasha's keen senses and combat skills would be useful in solving mysteries in a modern city. Another idea is to cross him with a magical school setting, where he has to learn new types of magic along with the students. Maybe he could also be crossed with a post - apocalyptic world, and his survival skills would come in handy for him and the other survivors.
One idea could be a scenario where Inuyasha and Naraku are forced to team up against a greater evil. Maybe a powerful demon from another realm arrives and threatens to destroy everything they both hold dear. They start off distrusting each other but gradually learn to work together as they realize they have no other choice.