Indeed, Koro Sensei passes away in the manga. This event is both emotional and crucial to the story's conclusion, leaving a lasting impression on readers.
They could start by having more conversations outside of work - related topics. This would allow them to bond on a personal level. For example, they could talk about their hobbies or past experiences. Karasuma might share his military training stories, and Koro - sensei could talk about his travels before coming to the school. As they get to know each other better, their relationship would develop into a more complex and interesting one.
Well, Koro Sensei used to be a human being who worked as an assassin. However, some top - secret experiments were carried out on him by the government. These experiments led to his transformation into a strange octopus - like form. His back story also includes the fact that he has a limited time to live because of the after - effects of those experiments, which is why he becomes a teacher to try and leave a positive mark on his students' lives before his end.
Koro Sensei himself is of course a very popular character. Since the fanfiction is about his human form, people are interested in seeing how his unique personality traits translate into a human appearance. His intelligence, his sense of humor, and his caring nature towards his students are all aspects that are explored.
Obviously, Koro Sensei in his human form is a very popular character. He's the center of most of these fanfictions as people are intrigued by how he would act and look like as a human. His students also remain popular characters. Nagisa, for instance, might have different interactions with human Koro Sensei, perhaps being more curious about his human past.
One interesting 'human Koro Sensei fanfiction' could be about Koro Sensei living a normal human life. He might be a teacher in a regular school, facing normal teaching challenges like dealing with difficult students or strict school regulations. For example, he could use his unique teaching methods to inspire a group of underachieving students to strive for better grades.
There could be a fanfiction where Koro Sensei in human form has to deal with his students in a completely different setting. For example, instead of teaching in a classroom, they are all on a survival adventure together. He uses his unique skills and knowledge, which he had even as a human, to protect and guide the students. It could explore his relationships with the students on a deeper level outside of the typical school environment.
In some koro sensei fan fiction, there are alternate timelines. For instance, in one timeline, Koro - sensei might not have been the target of assassination and instead becomes a full - time regular teacher at Kunugigaoka. This changes the dynamics of the entire story. The students grow in different ways, and there are new story arcs that revolve around the students' academic and personal development without the threat of their teacher's impending doom.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of various fanfictions, and you're likely to find some good koro sensei x aguri ones there.