Nestled in the peaks adjacent to the esteemed Kunugigaoka Middle School sits a small, neglected edifice accommodating the misbehaved and underachieving students of Class 3-E. The rest of the school body scorns these students, deeming their prospects of academic advancement dismal. However, when the government commissions them to vanquish their new instructor - the oceanic professor with tentacles, nicknamed "Koro-sensei," who has already obliterated the moon and plans to do the same to Earth by March next year - the Class 3-E students realize that their task is not child's play. In addition to Koro-sensei's supersonic velocity and invulnerable exterior, he happens to be one of the best instructors the students have encountered, tutoring them to surpass themselves as students and assassins. Undeterred, Nagisa Shiota and his cohorts must discover Koro-sensei's susceptibilities promptly, for the entire world's destiny hinges on their success.