Yes, there are some interesting 'Naruto Neko Highschool DxD' fanfictions. You can find them on popular fanfiction websites. Some may focus on crossovers between the Naruto and Highschool DxD universes with a neko (cat - like human) element added in for unique storylines.
The combination of different elements makes it unique. Naruto has its own set of powers, characters, and a ninja - based world. Highschool DxD has devils, angels, and a high - school setting with a different power structure. Adding the neko aspect gives it a new look, like having characters with cat - like features in these already distinct worlds.
First, give your Neko OC a distinct personality. For example, she could be really shy but have a hidden feisty side that only comes out when she's protecting her friends. Second, give her unique physical features. Maybe she has heterochromatic eyes, one blue and one green, which is rare among Nekos. Also, a special ability like super speed or the power to heal others quickly can make her stand out. And don't forget to give her a backstory that ties into the Highschool DxD universe, like she was an experiment by a rogue devil scientist.
The unique combination of the Highschool DxD universe and the Neko element. In the Highschool DxD world, there are already so many supernatural elements, and adding the Neko aspect brings in a new level of cuteness and mystery. It can lead to interesting character interactions, like how the regular characters in Highschool DxD would react to the Neko characters.
One idea could be a Neko OC who has a unique power, like the ability to control shadows. She could use this power to protect the main characters in secret, and as the story progresses, she gradually reveals herself and her motives. Another plot could involve a Neko OC from a different dimension who gets lost in the Highschool DxD world and has to find a way back while getting involved in the local supernatural affairs. Maybe she forms an unexpected alliance with a group of devils or angels.
You can try fanfiction websites like FanFiction.net or Archive of Our Own. They usually have a large collection of Highschool DxD Neko fanfictions. Just use the search function on these sites and type in 'Highschool DxD Neko' to get relevant results.
One idea could be that Naruto is somehow transported to the world of Highschool DxD. He could use his ninja skills and chakra in the new world, maybe even teach some of the characters there a thing or two about combat. For example, he could show Issei how to better control his power using chakra control techniques.
The storylines can be combined by creating a common threat. Suppose an enemy emerges that is interested in both the power of the Bijuu and the power sources in Highschool DxD. This would force the characters from both universes to team up. Also, the cultural differences between the Naruto world and the Highschool DxD world can be explored. Naruto could introduce concepts like ninja clans and shinobi training to the DxD characters, while they could introduce him to the complex social hierarchies and supernatural politics in their world.
The female characters from Highschool DxD, like Rias, would be intrigued by the unique personalities of the Naruto characters. Rias might see potential in some of them to join her peerage. And the Naruto girls, like Sakura, would be a bit shocked at first by the more revealing outfits and flirty nature of some of the Highschool DxD characters. But over time, they would bond over things like protecting their friends and the school. The Naruto boys would respect the power of the Highschool DxD devils and might even try to incorporate some of their fighting strategies into their own ninja combat styles.
In a Sharingan Naruto Highschool DxD fanfiction, the Sharingan could also play a role in terms of illusions. Imagine a scenario where the character uses Sharingan - based illusions to deceive the enemies from both worlds. They could make a Highschool DxD devil believe they are in a completely different environment like a dangerous Naruto - style forest filled with traps. And for Naruto characters, they could be made to see illusions of their worst nightmares or false threats from the Highschool DxD world, which would make for some really intense and engaging storylines.