Assassination Classroom Ansatsu Kyoushitsu

With Karasuma's help, E Class attends Kunugigaoka's graduation ceremony, where Nagisa learns that Koro-sensei had helped his parents get back together. When the mass media show up to try and interview the E Class about the assassination, Gakushu and the rest of A Class help them leave safely. As time passes and the E Class system is abolished, the students use their reward money to purchase the rights to the E Class campus mountain. Seven years later, several students get together to tidy up the campus building and discuss what everyone has been up to over the years. Meanwhile, Nagisa begins working as a trainee teacher at a delinquent high school, using the skills he had learned from Koro-sensei to set his class straight.

In the March of a certain year, a mysterious tentacled creature of unknown origin destroys over 70% of the moon, announcing that he will destroy the world in the same manner in one year. After several failed assassination attempts to kill him due to his Mach 20 speed, the government makes a deal with the creature to make him the teacher of Kunugigaoka Junior High School's Class 3-E, who are given specially designed weapons that can hurt the creature and offered a 10 billion yen reward to whoever can assassinate him before graduation. Although the students are generally frustrated with their failed assassination attempts, they discover the creature to be a respectable teacher in his own right. A group of students involve Nagisa Shiota, a boy with not much self worth, in their plan, in which they pin a grenade filled with creature-killing pellets to him and detonate it within range. However, at that moment, the creature sheds his skin, protecting both himself and Nagisa from the blast, threatening the other students not to use any more plans that harm others whilst also admiring Nagisa's efforts. To match their teacher's seemingly unkillable nature, classmate Kaede Kayano gives the creature the fitting name of "Koro-sensei".