Assassination Classroom

An inhuman nigh unkillable creature has decided to destroy the earth in less than a year. For some reason he has decided to become a teacher and under no circumstances will harm his students. His students now have to kill their teacher before he destroys the planet.

Assassination Classroom is a manga series written and illustrated by Yūsei Matsui. It originally ran in Shonen Jump from July 2012 to March 2016, and is licensed in North America by Viz Media. As of June 2016, twenty tankoubon volumes have been published in Japan, and it has had two anime adaptations, a single OVA episode in 2013, followed by a TV series in 2015.


 * Detonation Moon: And earth is next if Koro-sensei isn't killed soon enough.
 * Kryptonite Is Everywhere: To be fair, the threat that is Koro-sensei is a closely guarded secret and anyone other than world leaders let in on that secret is more likely than not supposed to kill him and has been supplied special weapons suitable solely for the task of killing him (in fact often these weapons are unsuitable for killing humans).
 * Nigh Invulnerability: Koro-sensei.