Inosuke is interesting as well. He was raised by wild boars and has a very wild and unruly nature. He is extremely competitive and has his own strange ways of fighting demons. His rough exterior but good heart make him a memorable character.
Zenitsu is quite interesting. His cowardly nature at first, which is in contrast to his amazing lightning - based fighting skills when he's unconscious, creates a lot of comical and engaging moments in the light novel. Inosuke is also fascinating with his wild and boar - headed appearance and his brute - force fighting style.
The Goblin Slayer himself is quite interesting. His single - minded focus on killing goblins and his rather stoic personality make him stand out. Then there's Priestess. Her growth from a novice to a more confident adventurer is engaging.
Buffy herself is very interesting. She's a strong, independent girl who has to deal with both high school drama and vampire slaying. Spike is also cool. He's a vampire with a complex personality, sometimes an enemy, sometimes an ally. And Willow, Buffy's friend, is interesting too. She has her own journey with magic.
I think Giles is one of the most interesting characters. He's Buffy's Watcher, guiding her in her slayer duties. He has a lot of knowledge about the supernatural. Another interesting character is Faith. She's also a slayer, but she has a much darker side compared to Buffy. And Angel, the vampire with a soul, his inner struggle between his vampire nature and his human side makes him really engaging.
One interesting character could be a Devil Slayer who has the power to manipulate shadows. He can use the darkness not only to attack demons but also to move stealthily. His backstory of how he got his powers, perhaps from a fateful encounter with a shadow - based demon, makes him really engaging.
The world - building is another aspect. Writers often blend the ninja world of Naruto with the demon - infested world of Demon Slayer. They create new landscapes, rules, and cultures that are a blend of both universes, which is really engaging to read about.
Sasuke could be really interesting in this style of fanfic. His natural inclination towards the darker side in the original Naruto could be further explored. He might take on even more extreme actions and develop new powers related to the dark slayer concept.
There are several interesting characters. For example, the teacher figure in the story. He has a wealth of knowledge and his own secrets. He guides the protagonist in many ways. Then there are the antagonists who are not just one - dimensional villains. They have their reasons for doing what they do, which makes them complex and interesting. The way they interact with the protagonist and other characters adds depth to the story.
The side characters who oppose the protagonist can be quite interesting too. They often represent the status quo or the forces that the protagonist has to overcome. Their motives and the lengths they go to stop the protagonist add depth to the story.
The main demon protagonist is likely to be very interesting. He or she is probably on a journey to achieve supremacy, which means facing numerous challenges and opponents. There might also be a wise old demon who acts as a mentor or an obstacle, depending on the situation.