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!

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.

The brilliant, belligerent Karma Akabane, Nagisa's former classmate, joins 3-E and immediately jumps into the assassination mission with both feet.

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?

Before the torturous school assembly begins, Okuda attempts to poison Koro Sensei in an unexpected way... with unexpected results.

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.

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.

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.

A new student joins the E Class with a singleminded focus on assassination that drives her classmates to distraction. Koro Sensei to the rescue!

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. Hoping to prove him wrong, Koro-sensei proposes a match between Irina and Lovro to see who will be the first to 'kill' Karasuma, offering Karasuma his own incentive should neither win. Despite Lovro's doubts after he fails to kill Karasuma himself, Irina manages to use what she's learned targeting Koro-sensei to get close, with Karasuma accepting defeat at her hands and Lovro acknowledging her efforts. Later, Nagisa, Karma, and Ritsu accompany Koro-sensei on a mach speed trip to Hawaii to watch the premiere of a new movie, getting a lecture along the way and learning a lot more about Koro-sensei's point of view. On their way back, a man in a while cloak observes alongside a boy, the second transfer student who claims to be Koro-sensei's brother.

Class 3-E prepare for the arrival of their second transfer student, who is allegedly more powerful than Ritsu. At that moment, a white-robed man named Shiro arrives with the new student, Itona Horibe, who claims to be Koro-sensei's younger brother. When Itona faces against Koro-sensei later that day, it is revealed that he possesses the same kinda of tentacles Koro-sensei has in his hair. While Shiro uses his knowledge of Koro-sensei's weaknesses to give Itona the advantage, Koro-sensei takes advantage of that Itona's tentacles are identical to his and uses Anti-Sensei knives against them, allowing him to knock Itona out of the ring and win the match. When Itona reacts negatively to the thought of studying and tries to counterattack, Shiro knocks him out and takes him back with him. Afterwards, the class try to ask Koro-sensei about how he and Itona are connected, but he remains tight-lipped, stating they must use assassination to find the answers they seek. The students, determined to kill Koro-sensei before anyone else, decide to have Karasuma teach them more assassination techniques.

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. Despite knowing the odds are against them, particularly when pitted against the club captain Shindo, Sugino remains determined to win, prompting Koro-sensei to coach them for the match, teaching them how to go up against his mach speed fastballs. On the day of the match, Class 3-E use a bunting strategy to load the bases, allowing them to get an early lead. Not willing to let this slide, Asano takes over as the baseball club's coach to put a stop to Class 3-E's bunting strategy, using the power of hypnotic suggestion to turn Shindo into a bloodthirsty warrior. With the bases loaded against them, Class 3-E manage to use some provocations Karma made concerning some unfair play earlier to their own advantage, placing some of their player up close to Shindo to prevent him from swinging without hurting them, allowing Class-E to win the match. Afterwards. Sugino expresses how he wanted to show off the friends he made in Class 3-E, managing to rekindle his old friendship with Shindo.

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. While initially proving popular with the students to do his light-hearted personality, they soon learn his true nature as a ruthless and sadistic instructor who uses fear and violence to train his pupils. When Karasuma voices his objection, Takaoka challenges him to pick one of his students to face off against him using a real knife. Placing his faith in the aura he felt before, Karasuma nominates Nagisa to fight against Takaoka. Following Karasuma's advice and going against Takaoka's expectations of being afraid of wielding a knife, Nagisa uses the assassination skills he had learned and manages to get the upper hand on Takaoka, winning the match. When Takaoka violently objects to defeat, Karasuma beats him back while Asano fires him, with Karasuma returning to his usual teaching position.

Koro Sensei exposes a major weakness, and Terasaka interrupts a fun summer day out with an assassination attempt that goes a little too far.

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.

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.

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.

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?

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 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.

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.

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. Despite being heavily beaten by Takaoka, Nagisa uses what he learned from Lovro to perform his secret technique; shocking Takaoka with a sudden clap before using the stun-gun Terasaka gave him to bring him to his knees, leaving him with the smile he fears so much before shocking him unconscious. Afterwards, the three assassins from earlier reveal the virus they used is nothing more than an enhanced food-poisoning bug that will wear off eventually, as they didn't agree with Takaoka's methods. The next day, after the affected students recover from their symptoms and Koro-sensei emerges from his crystallized state, the students makes the most of the remainder of their vacation before returning to school for the second term of their assassination classroom.