One common theme is loyalty. Hayate is always loyal to Nagi in the series, and this is often explored further in fanfiction. For example, how far he will go to protect her.
One interesting fanfiction could be where Hayate gets involved in a special mission within the Naruto universe that was not in the original story. It might explore his combat skills in a new and exciting way.
One great 'Nagi x Hayate' fanfiction is 'A Chance Encounter'. It beautifully portrays the relationship between Nagi and Hayate, with vivid descriptions of their interactions. The author does an excellent job of showing Nagi's dependence on Hayate in a really heartwarming way.
Another popular trope is the 'found family' one. Hayate could form bonds with other characters in the Naruto world, creating a sense of family. This can be really heart - warming in the context of the often - dangerous Naruto universe.
A 'combat butler fanfic' could have a plot where the butler is not human, but an android created for combat and serving. His master, a young heir to a large company, discovers his true nature and they have to deal with the implications. The butler then has to fight off other androids sent by a rival company to kidnap the master. This could explore themes of identity, loyalty, and the relationship between technology and humanity. There could also be cool action scenes where the combat butler shows off his advanced combat capabilities and uses his built - in gadgets to overcome the threats.
One popular character could be a young, headstrong master who constantly gets into trouble and needs the combat butler to bail them out. Another might be an old - fashioned butler trainer who taught the combat butler all his skills. Also, a villainous character like a mafia boss who is constantly trying to undermine the master and the combat butler's efforts to protect them.
Another aspect of the training could be mental discipline. Hayate may introduce Naruto to meditation - like techniques to help him focus his chakra more effectively. He'd also likely teach Naruto how to keep a calm head in the heat of battle, sharing his own experiences to illustrate the importance of mental fortitude.
Well, in many fanfictions, Naruto might use his chakra to heal Hayate. Since Naruto has a large amount of chakra and has learned some healing techniques over time, he could transfer his chakra into Hayate's body to repair the damaged parts.
Another problem might be the lack of proper resources. Even if Naruto has the ability to heal, he may not have all the necessary herbs or medical equipment. In the world of Naruto, some healing requires specific items. If they are in a remote location or in a battle - torn area, getting these resources could be a huge hurdle.