A class of junior high "misfit" students who are tasked with assassinating their new teacher, an octopus-like creature nicknamed Koro-sensei, who destroyed the moon and threatens to destroy Earth in a year. The students have to learn to balance their assassination attempts with the lessons from Koro-sensei, who is surprisingly an excellent teacher, while the government offers a ¥10 billion reward for his head. Each episode often focuses on individual students, their growth, and their internal conflicts between wanting to kill their teacher and growing to care for him.

When the Ministry of Education goes back on its promise to keep Ooarai Girls Academy open, the task of saving the five-mile-long Academy Ship from the wreckers falls to Miho and her barely-seasoned tankery team. However, things go off track almost immediately. While the Oorai tank crew may have won the high school tournament, they’re now facing a larger and more experienced university team, and if they fail, their armored vehicles will be forfeit! Will they be swapping their tanks for the memories? It’s possible, but winning a tank battle is all about tactics and teamwork, and the fledgling Ooarai students have more friends and allies than anyone suspects.