Season 1
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.
Assassination Time
A creature who blasted the moon into a crescent shows up at Kunugigaoka Junior High School--and he's giving the students a year to assassinate him!
Baseball Time
The reasoning behind the E Class's segregation is revealed. Nagisa tracks Koro Sensei's weak points in the hopes of using them to take him down.
Karma Time
The brilliant, belligerent Karma Akabane, Nagisa's former classmate, joins 3-E and immediately jumps into the assassination mission with both feet.
Grown-Up Time
A new foreign-language teacher comes to 3-E with some major ulterior motives... among other things. Will she get any closer to killing Koro Sensei?
Assembly Time
Before the torturous school assembly begins, Okuda attempts to poison Koro Sensei in an unexpected way... with unexpected results.
Test Time
Time for midterms! Koro Sensei gives his aspiring assassins an ultimatum as they battle a grueling test and the disdain of the rest of the school.
School Trip Time, First Period
The students go on a school trip to Kyoto, where they must still keep assassination foremost in their minds. Kanzaki faces trouble from her past.
School Trip Time, Second Period
The E Class gives a pro sniper plenty of chances to take down Koro Sensei, then try to make the most of what's left of their school trip to Kyoto.
Transfer Student Time
A new student joins the E Class with a singleminded focus on assassination that drives her classmates to distraction. Koro Sensei to the rescue!
L and R Time
Irina is greeted by her former master, retired assassin Lovro, who thinks she should give up as she has no chance of killing Koro-sensei.
Transfer Student Time, Second Period
Class 3-E prepare for the arrival of their second transfer student, who is allegedly more powerful than Ritsu.
Ball Game Tournament Time
A baseball tournament is to be held, in which Class 3-E are forced to play an exhibition match against the top players of the school's baseball club, which Sugino used to be a part of.
Talent Time
As Karasuma briefly senses what appears to be a fearsome aura coming from Nagisa, Akira Takaoka, an aquaintance of Karasuma from the Ministry of Defense, is sent to Class 3-E to take over Karasuma's role as P.E. teacher.
Vision Time
Koro Sensei exposes a major weakness, and Terasaka interrupts a fun summer day out with an assassination attempt that goes a little too far.
End-of-Term Time
For finals, Koro Sensei gives his class a new goal--with an irresistible reward. The E Class makes its own deal with the top-tier A Class's Big Five.
School's Out - First Term
After two days of exams, the results are in. Both the ace A Class and the end E Class must come to terms with the outcome--and so must Koro Sensei.
Island Time
The E Class trains intently under a pro killer to prepare for their island assassination. Once there, they must make sure everything falls into place.
Action Time
The summer assassination attempt is followed by a crisis affecting nearly half the E Class. Can the rest think and move fast enough to save them?
Pandemonium Time
The E Class must put their lessons into practice as they tackle an intimidating hotel brimming with baddies--and all without Koro Sensei's help.
Karma Time, Second Period
Karma must use his head to get past a formidable foe. Nagisa goes undercover as the E Class continues to sneak its way to the hotel's top floor.
XX Time
The students take on one last assassin opponent before meeting the shadowy figure who's holding the virus remedy hostage in exhange for Koro Sensei.
Nagisa Time
Before Nagisa completely gives into his anger, Terasaka throws a stun-gun at him, urging him not to become a murderer and think about what's truly important.