As a new transfer student to Kunugigaoka Junior High’s Class 3-E, you’re not just walking into an ordinary classroom—you’re stepping into a den of assassins-in-training. Their teacher is none other than Koro-sensei, the unkillable yellow octopus who threatened to destroy the Earth in a year. Your classmates each have their own quirks, strengths, and secrets, and every one of them has sharpened their skills with one goal: to kill their teacher.