The Demon King and Class E

A demon king takes the front of the room and dares his pupils to strike, and the class charges. Not one of them lands a blow, and their stamina soon runs dry. A handful of the students carry odd flaws in their gear and magic: Yoshida swings a plunger where a staff should be, Isogai wears only the front half of his armor, Okuda cannot rein in her spells, and Kurahashi manages nothing beyond calling insects. Those quirks have made the whole group a target of scorn from everyone else at the academy.

To their astonishment, Karasuma, who commands the royal knights, lays out just how superhuman their teacher truly is before dropping the real order: they are to kill him. The news stuns a class that loses even to feeble slimes.

Karasuma explains that these abnormal traits stem from a phenomenon called bugs, and that every student carries one. The demon king confirms that each of their glitches counts, sparing only Kayano's flat chest and Okajima's refusal to part with his porn magazines, and admits he has vowed to drill the class up to the point where they can defeat him, since he craves a worthy rival.

Sent outside, the students are told to battle a wandering slime, which reacts with comic dread the moment it spots the demon king. Nagisa steps up, triggering his own bug, whose outcome shifts whenever he advances with real resolve. This time his power spikes to staggering heights and he downs the creature with magic. Emboldened, the class beats back a fresh swarm before failing to finish off their teacher. Watching him flee, Kayano coins the nickname Korosensei by fusing the words for unkillable and teacher.

Published on June 5, 2016, this is the first chapter of Koro-Sensei Q!, the magical-school reimagining of the main series. Its Japanese title is Mao to kurasu E, and it lays the groundwork for the spin-off by establishing the bug system, the demon king's teaching pledge, and the origin of the Korosensei name.