|The E Class and the Demon King|
|Romaji||Maō to E-gumi|
|Next Episode||The Red Devil|
|Japanese||December 23, 2016|
|English||January 11, 2017|
|Ending||Seishun Satsubatsuron Remix|
The E Class and the Demon King is the first episode of the Koro-Sensei Quest! anime. The episode first aired in December 23, 2016.
In the alternate universe set in RPG world, the students of Kunugigaoka Magical Academy are heroes under training and students of class 3-E are those with bugs - making them weaker than other heroes. They are tasked to defeat Koro-sensei, a demon lord who intentionally teaches them so they could defeat him one day.
The Demon King first arrives in Class 3-E homeroom to start class with their students and waits for his students to attack him as he greets them.
The Class 3-E is later shown very tired after trying to attack the Demon King. Later the Demon King was mentioning how the class had a long way to go, with the class complaining that they couldn't take him down because of their low levels and bad equipment.
Several examples why the class couldn't beat the Demon King were shown, with one of them being that Yoshida could only equip bathroom tools as weapons and another being that Isogai could only buy the front half of a suit of armor.
A flashback of Class 3-E meeting the Demon King and Commander Karasuma explains why the class has these quirks, with Commander Karasuma explaining that these quirks were bugs and that these bugs were the key to defeating the Demon King. The Demon King then explained why he wanted to train them; so he could fight someone on an equal footing with him. Finally, the class introduction ended with Fuwa breaking the fourth wall when asking about limits, the reference to the popularity being how people will choose who quits first based on a vote, along with a new name for the Demon King: Koro-sensei.
As training is started by the Demon King, a scene is shown where Takebayashi breaks down after the principal Gakuho Asano publicly humiliates him with a public announcement, bringing Takebayashi into Class 3-E.
The episode then returns to Koro-sensei and his current students, where Koro-sensei is introducing them to their new archenemy; the slime. At first, when the slimes see Koro-sensei, they start to admire and try to please him (For Koro-sensei is the Demon King). But after hearing that he wants to sacrifice them to the humans instead, they immediately start to run, with the class trying to catch them. At first, the hunt against the slime doesn't go well; however, after Nagisa's randomized bug is activated, they manage to defeat the slimes with ease after Nagisa uses a fire spell to scare them. However, Nagisa isn't able to change back after this, having to ask Koro-sensei for help on the matter.