One possible plot could be that Naruto is somehow transported to the world of 'One hell of a butler' and has to adapt to being a butler. He might use his ninja skills in unexpected ways while serving the master there. For example, using his shadow clone jutsu to do multiple tasks at once.
Well, I'm not entirely sure. Fanfiction is a vast and diverse world. There could be some amazing 'Naruto is one hell of a butler fanfiction' out there. It could be that an author has created a really unique story by combining the two universes. Maybe they've made Naruto a butler in some strange and exciting way. But you'd have to search through different fanfiction platforms to find out for sure.
The butler could be a protector. He might use his skills, like combat skills or knowledge of ninjutsu, to keep Naruto safe from various threats, whether it's rogue ninjas or political schemes.
Sakura might be initially suspicious. She is a smart girl and would wonder about the butler's intentions. She might keep a close eye on him to make sure he doesn't harm Naruto in any way.
One interesting Naruto and Hell Girl fanfiction could be where Naruto somehow ends up in the world of Hell Girl. Maybe he meets Ai Enma and tries to convince her to use her powers for good in a different way. There could be a plot where Naruto's positive energy starts to influence the dark world of Hell Girl.
In Naruto fanfiction related to Hell, one rule could be that the powers and abilities of characters are often adjusted to fit the Hellish environment. For example, a character might gain the ability to withstand extreme heat or manipulate demonic energy.
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.
One common theme could be the clash of different power systems. Naruto has its chakra - based ninja abilities and Lucy Butler might have her own set of powers. Writers may explore how these two power systems interact or conflict. Another theme could be the characters' moral compasses. Naruto is often about good vs evil in the ninja world, and when Lucy Butler is added, it could create new moral dilemmas.
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.