When I discovered the manga version of this book and was then inspired to learn about the mysterious and yet slightly creepy smile on the front cover, the short summary did prompt me to watch the anime. The simply hilarious idea that in a classroom full of assassins the goal is to kill your teacher. While one would first consider this anime to fall into the category of mystery/thriller, this preconception is contrasted by the personality of this teacher. Koro-Sensei (the unkillable teacher) is the best teacher the class ever had. The 3E that Koro-Sensei teaches is a class full of those who were considered too bad to continue on the main campus and were thus sent away to a smaller, older and secluded school campus. Before Koro-Sensei's arrival they seemingly had no chance of ever returning to the main campus as there was basically no suitable teacher wishing to help them. Koro-Sensei, on the other hand, is a teacher who takes it up as a challenge to change and help the students.
Now comes the question: Why should they try to kill Koro-Sensei if he is such a good teacher? Well the answer is quite as hilarious as the act by itself. He is a supernatural being who after the moon exploded claims to have caused it to do so and threatens to destroy the Earth in one year's time. For some reason (later revealed in the 2nd season) he wishes to teach the 3E of this school. The next question that of course arises at this point: Why don't they simply kill him? Well, he can travel at Mach 20 and thus so fast that no assassin so far was able to kill him. Using the children at the school might at least give the government the chance of keeping an eye on him.
And thus, coming from this comical and awkward background a wonderful story that demonstrates much more than the simple setting implies. Not only does the series creatively shows how this teacher may be their assassination target, but also their friend. The characters of the series evolve as well creating a spirit of community and hope within the students. Koro-Sensei on the other helps people to get better in their thinking and appears almost human with all of his faults. His superhuman nature on the other not only becomes visible when seeing his physical make, but also the extreme devotion with which he treats his students.
Overall, the setting allows for a very entertaining, comical and also fun storyline to evolve from there. The anime is able to make the best from all of this making the anime effectively not only about assassination techniques, but essentially about how this community is able to work together when they are set against discrimination and harassment from the main campus. This anime has become one of my favourite anime because it exhibits how communities can work together and how individuals can advance themselves by trusting their own talent. Besides the hilariousness of the situation, the anime thus also gains a serious message that can be taken as a life motto.