Another concept could be a story where the Akatsuki from Naruto are after the power of the Pandora Hearts world. They believe that the power of the Chains could help them achieve their goals in the Naruto world. So they infiltrate the Pandora Hearts world, causing chaos as they try to capture the most powerful Chains.
A fanfiction could explore a scenario where the Sharingan in Naruto has a connection to the power of the Pandora Hearts world. Maybe Sasuke discovers that his Sharingan has a hidden ability that is related to the power of the Chains. This could lead to a whole new arc in his character development as he tries to understand this strange connection.
One common theme is the struggle against fate. In Naruto, Naruto himself is constantly fighting against the pre - determined path set for him as a jinchuriki. Similarly, in Pandora Hearts, the characters are often at the mercy of the Abyss and their pre - ordained roles. In fanfictions, this theme gets explored further as characters from both universes might come together to resist their fates.
An interesting Pandora Hearts OC fanfiction idea could be an OC that is a hybrid of a human and a Chain. This OC could struggle with their identity, being neither fully human nor fully a Chain. They could be on a journey to find out where they truly belong. Also, an OC that is a time - traveler who has come to the Pandora Hearts world to prevent a certain catastrophe from happening could make for a great story.
Magic and chakra could be combined. In the fanfiction, it could be that the power of the Chains in Pandora Hearts can be harnessed using chakra. So a character like Kakashi could figure out a way to use his Sharingan to control a Chain, creating a unique fighting style that combines the two fictional universes.
Perhaps Fem Harry Potter is mistaken for a Keyblade wielder at first. She has to prove herself in the Kingdom Hearts universe while also trying to find a way back to her own world. Along the way, she discovers that there are similarities between the magic in her world and the power of the Keyblades.
One idea could be a fanfic that focuses on the backstories of the minor characters in Pandora Hearts. For example, exploring the past of some of the servants in the Vessalius household. Another idea is a time - travel fanfic where a character goes back in time to change a crucial event in the Pandora Hearts story. Maybe a fanfic that imagines an alternate ending to the series, where different alliances are formed and different fates await the characters.
One idea could be a crossover where characters from both universes meet in a magical realm. For example, Harry Potter characters could find themselves in the world of Pandora Hearts and have to deal with the strange creatures and the complex power dynamics there. Another idea is a story where the magic systems of both worlds combine in unexpected ways. Maybe a Hogwarts student discovers a Pandora Hearts - style power within themselves.
One idea could be to have characters from Naruto end up in the world of Danmachi. For example, Naruto himself could find his way into the dungeon and his ninja skills would be put to the test against the dungeon monsters. His shadow clone jutsu could be used in interesting ways, like sending clones into different dungeon levels to scout or fight. Another idea is to have the concept of chakra introduced into the Danmachi world. This could change the way adventurers fight and level up. Maybe some of the Naruto characters could train the Danmachi adventurers in new combat techniques.
One idea could be a crossover where Naruto is somehow transported to the Star Wars universe and meets Padme. Maybe he uses his ninja skills to protect her from the Sith.
Another concept is that Naruto is sent to Middle - earth. There, he could use his ninja skills and chakra powers. He and Gandalf could team up to fight Sauron. Naruto's ability to make friends and inspire others would be really useful in uniting the different races of Middle - earth against the common enemy.
A more complex idea is that the Matrix is used to create a virtual training ground for the shinobi. They enter the Matrix to practice their skills in a more controlled environment. However, they soon realize that there are some dark secrets within the Matrix, and Naruto has to lead the way to uncover the truth and free those who are trapped inside.