The unique feature is the combination of two very different universes. Naruto's world is full of ninjas, chakra, and big - scale battles, while the Black Butler world is more about Victorian - era mystery, demons, and the underworld. When combined in fanfiction, it creates a whole new set of scenarios.
Character growth is also a common theme. Characters from both series are put in new situations. Naruto might have to adapt to the strict social hierarchies in the Black Butler world, and characters from Black Butler might learn from Naruto's values of friendship and determination. This allows for a lot of character development and makes the fanfictions more engaging as we see familiar characters evolving in new ways.
First, you need to do your research on both universes. Know the characters, their powers, and the settings well. For example, know all about Naruto's jutsus and Sebastian's demonic abilities. Then, think of a good plot device to bring the two worlds together. It could be a portal or a powerful spell. After that, start with an interesting introduction that hooks the reader, like Naruto suddenly finding himself in the Black Butler's Victorian - era London.
Power dynamics is another theme. Naruto is a very powerful shinobi and in the Black Butler world, there are different power hierarchies. Fanfictions often play with how Naruto's power fits in or disrupts the existing power structures in the Black Butler universe. For example, how he might deal with demons or the Queen's orders. And also, friendship is a theme. Characters from both series form unexpected friendships, like Naruto befriending Sebastian. Their different personalities and goals make these friendships interesting to read about.
It could be really interesting. Sebastian from Black Butler might find Naruto's ninja world full of chaos and yet fascinating. He could use his butler skills to blend in, while Naruto might be intrigued by Sebastian's elegance and power. Maybe Sebastian would be tasked with protecting Naruto for some strange reason, like a contract made by the Hidden Leaf Village elders.
One interesting crossover could be Naruto ending up in the Black Butler universe and having to deal with the complex social hierarchy and supernatural elements there. He might use his ninja skills to fight off demons or other threats that Sebastian and Ciel face. Another could be Sebastian being intrigued by Naruto's chakra and trying to figure out how to use it for his own purposes in serving Ciel.
There is a fanfiction titled 'Black Butler Meets Naruto: Crossover of Worlds'. In this, the author does a wonderful job of bringing characters from both series together. Sebastian, from Black Butler, is especially fascinating when dealing with Naruto's ninja world chaos. It has some really cool fight scenes where the unique abilities of both universes collide.
One great 'naruto black butler fanfiction' is 'Naruto in the Black Butler World'. It has an interesting plot where Naruto is suddenly transported to the Black Butler universe and has to adapt to the new and rather dark environment. He uses his ninja skills in unique ways to deal with the various challenges there.
Yes, of course. Their unique personalities and relationships in the original work are the main sources of inspiration for fanfiction writers. Writers often base their stories on the existing characters' traits and the chemistry between them.