"A group of junior high students are joyfully discussing an assassination. If you look at it normally, this is the pinnacle of madness."
The story is about class 3-E of Kunugigaoka Middle School where every morning they greet their sensei (named Koro-sensei) with a massive firing squad. The sensei is a weird combination of an alien and an octopus that moves at speeds of mach-20. It turns out this creature was responsible for the destruction of the moon, rendering it forever in a crescent shape. He has announced that he will destroy the world in one year. The creature will teach class 3-E how to assassinate him before the year is over. But...he's the best teacher they've ever had.Imagine Great Teacher Onizuka mixed with sci-fi and espionage to get an idea of what you're in for. The series creator is also the creator of Majin Tantei Nougami Neuro, which deals with similar ideas, mainly a supernatural creature with Blue and Orange Morality who's ultimately bettering the people it comes across. The difference is where Neuro was protecting his food source, Koro-sensei is trying to better his students by working in the killing arts as a teaching tool. And it works. Course there is the problem of him planning to destroy the world...Ansatsu Kyoushitsu is currently serialized in Weekly Shonen Jump.The character page is in the development stages.
This series provides examples of:
The Ace: Karma in regards to class E, Koro-sensei for the entire series.
Nagisa when it comes to assassinations, surprisingly enough.
Affably Evil: For a man (for a given value of "man") who wants to destroy the world, Koro-sensei doesn't act like it.
A.I. Is a Crapshoot: Ristu: designed as a learning AI-unit dedicated to assassination with a carefully simulated and bounded personality. Decided she preferred being a Moe student against orders when she got a personality upgrade (although, still quite happy to lend a helping hand to try destroying Koro-sensei).
Animal Motif: The Chairman has a centipede for his animal motif, as does his son.
"There isn't a single student stronger than him in this school.'" speaking with regards to the Chairman's son.
*cut to a yawning Karma*
Arc Symbol: The crescent moon on Koro-sensei's tie. It's often used as a reminder of just how powerful Koro-sensei is.
Applied Phlebotinum: The guns, grenades, knives, swords, etc. used by the students are made of a specially made substance harmless to humans, but on contact will cause Koro-sensei's cells to break down.
Assassin Outclassin': Naturally, or the Series would be over before hitting the third page of the first chapter.
Assassins Are Always Betrayed: The fact that nobody got hurt when Shiro blew up a pool that most of class E was swimming in required a good deal of luck. The intention may not have been to hurt them, but it was clearly negligent of their safety.
A-Team Firing: The opening of the story begins with the entire class trying to gun Koro-sensei down. Not only does this fail, but Koro-sensei continues as if nothing were happening, taking attendance as the class continues shooting. The only notice he takes is when he asks a student to speak up, since he can't hear well over the gunfire.
Axes at School: They're rubber knives and pellet guns that are only harmful to Koro-sensei, but they're still rather alarming.
Bad Ass: Karma. He is the very first student to actually inflict damage on Koro-sensei as well as causing him to (momentarily) lose his cool.
Karasuma is also a wonderful example, apparently scoring a full 100 in "fighting" by the assessment of Irina's assassination master. And then there's his attitude, which is also undeniably Badass.
Badass Boast: After blowing off Koro-sensei's index finger, the AI delivers this.
AI: The killing probability of the next shot is less than 0.001%. The killing probability of the shot after that is less than 0.003%. The probability that I'll be able to kill you by graduation is more than 90%.
Beach Episode: In chapter 43, Koro-sensei builds a pool for the students so they can find relief from the summer heat. This manages to tie in to the main plot when it leads to them discovering that Koro-sensei can't swim.
Beauty Equals Goodness: If you're attractive without looking downright creepy, then you're likely a member of Class-E in one way or another. The only exception to this seems to be Koro-sensei and the three Class-E bullies. It's even lampshaded when two girls in a higher-ranking class note that Class-E's phys ed teacher, the young government agent Tadaomi, is rather attractive, and that all of the guys and teachers in their class are ugly and mean.
Played With Takaoka: his cartoony (well, more cartoony) smiley face masks a vicious streak a mile wide.
Berserk Button: When Bitch-sensei calls Class E "Misfits of the school" and tells them studying would be meaningless, she gets pelted with school supplies by the whole class.
Also Koro-sensei if anyone tries to hurt his children. Usually though he just 'beautifies' them, calling it 'maintenance'. Then again, he also called it performance when he beat up several wannabe-kidnappers...
When he saw Horibe Itona's tentacles, his face goes Pitch Black, Extreme Anger.
Blatant Lies: When higher-ranked students harass Nagisa because they didn't like how happy he seemed, they corner him. When he doesn't seem threatened or bothered by him, they threaten his life. All it takes is a non-threatening Wham Line and a Death Glare on Nagisa's part to scare them off. Then they go and tell everyone that they were the ones given a death threat.
Boke and Tsukkomi Routine: Invoked. The students occasionally mention wanting to "tsukkomi" in response to whatever ludicrous situation they've just been presented with.
Takebayashi, do you seriously want that to be your first line in this manga?!
Break the Haughty: Karma gets a little too proud of his early successes against Koro-sensei. However, all he really managed to do was draw Koro-sensei's full attention to him, and Koro-sensei makes sure that he knows exactly how outmatched he is by dealing with his attempts in the the most offhand and humiliating ways he can, until Karma is Driven ToSuicide Attack. Fortunately for him, Koro-sensei always fixes what he breaks.
Chapter 54 has this happening to Karma (again) and Gakushuu Asano.
Bunny-Ears Lawyer: Koro-sensei, despite his appearance, despite being a god-like superbeing capable of destroying planets... is actually a really great teacher.
Curb-Stomp Battle: Akira Takaoka, elite soldier and special forces instructor, versus Nagisa Shiota, 14 year old middle school student with three months of assassin training. Nagisa wins in under 10 seconds.
Detonation Moon: Koro-sensei's first major demonstration of power: he basically reduced it to a permanent crescent by destroying 70 percent of its volume.
Did You Just Flip Off Cthulhu?: Not flipping him off, but scolding him, which is in line with the spirit of the trope. Megu, Yada and Fuwa give Koro-sensei a pretty good telling off when he pulls up class E's flower bed as part of an attempt to look cool. They make him replant the whole thing at regular speed as punishment. Afterwards, the class holds an assassination rally with a handicap: Koro-sensei gets tied up and dangled from a tree branch like a pinata while the class tries to hit him with anti-sensei knives taped to long poles.
Dissonant Serenity: Takaoka's always grinning, whether he's handing out pastries, revealing his ridiculous training schedule, or violently attacking contrary students.
Nagisa is capable of this as he's remarkably talented in controlling his bloodlust.
Doorstopper: What Koro-sensei produces every time he comes up with a "guidebook" for class excursions. One octopoid's guide is another man's industrialised carbon capture method—with indices, cross-references, info-panels, bullet points and plot-significance.
Drill Sergeant Nasty: Takaoka Akira. Has a "9-sticks-to-one-carrot" philosophy, is more like a dictator than an officer, and "accidentally" leaves a picture of the soldiers he's tortured in front of Tadaomi. And he's always smiling.
Dutch Angle: The panel where Nagisa's visible killing intent goes from 0 to 100 in an instant is drawn like this.
Easter Egg: On the newspaper page with the baseball player being attacked by Koro-sensei's tentacles there's a side article captioned by the quote "My wife is slut".
Eldritch Abomination: Averted. Even though Koro-sensei looks like a freaky alien octopus, he states that he was born and raised on earth. As what, human, animal, vegetable, or mineral, is anyone's guess.
Embarrassing Nickname: Irina Jelavic gets two rather funny ones from the students after she insults them. 'Bitch-neesan' and 'Bitch-sensei' after she finally (sort of) wins their approval.
The End Justifies The Means: The Principal makes Class E the school's pariahs because it means the other students will do anything to keep their grades up and not get sent there.
Takaoka's extremely harsh (if not downright impossible) training schedule will be worth it if just one student survives and succeeds in killing Koro-sensei because Takaoka will become famous for training the assassin and then Tadaomi will finally acknowledge his superiority!
Excuse Me While I Multitask: When people try to kill Koro-sensei he's usually doing other things, such as meticulously trim his attackers eyebrows or give a fighter jet a polish in mid-air. See also the example from A-Team Firing.
Self-Duplication: He can move so fast he can make selectively tangible afterimages. Chapter 12 shows him making one for every student in the class to personally focus on their weak subjects. He even leaves one outside to rest from all that work.
Even Evil Has Standards: Koro-sensei is not pleased when one of his students' collaborative attempt at killing him almost injures one of their own.
The other students' treatment of Class E at the assembly appalls even Bitch-sensei.
A Father to His Men: How Takaoka sees himself. The torture and possible mind-rape is just fatherly discipline!
Fictional Sport: The students play assassination badminton, which is actually more like volleyball in almost every way. The main differences are that they can only touch the ball with the blade of a knife, and they use a tennis net instead of a badminton or volleyball net.
Flash Step: Koro-sensei has a top speed of Mach 20. During one assassination attempt, he easily dodged the attacker while meticulously trimming his attacker's eyebrows. When attacked by state of the art fighter jets, he gave them a mid-air waxing. When attacked by knife armed students, he disarmed all of them, then replaced the knives with tulips without their noticing.
Forceful Kiss: Irina does a 30-hit combo one to Nagisa at one point before telling him to meet her in his office so they can discuss Koro-sensei's weaknesses.
A Form You Are Comfortable With: Debatable, but the first chapter makes it clear that his current appearance is not his true form. Surprisingly, sans tentacles, his shadowy true form seems human-like.
Foreshadowing: Nagisa is being built up to have a lot of hidden talent.
Confirmed in Chapter 41 which reveals that Nagisa has an exceptional talent for assassination. To be specific, his ability to hide such bloodlust that it scares trained soldiers.
In chapter 28, Kuro-Sensei takes several students to see an American superhero movie, wherein the major Plot Twist involves the Big Bad being revealed to be the heroine's brother. At the end of the chapter we meet Itona, Kuro-Sensei's Ax-Crazy younger brother.
Game Face: Koro-Sensei's Black Face. When it turns Black, it is on.
Gratuitous IPA English: On the cover page of chapter 55, the word assassination is rendered as əsˈęsənˌeɪʃən, which would actually be assassanation, with the first "ass" as its own syllable. The correct rendering would be əˈsęs.ɪnˌeɪ.ʃən. Let this stand forever as the most pedantic entry on the page.
Green-Eyed Monster: Takaoka Akira was incredibly jealous of Tadaomi, as Tasaomi was the most talented member of their unit in the JSDF and quickly rose above him. He hopes that if he turns Class E into the heroes who will defeat Koro-Sensei, then he'll also become a hero, and finally be able to order Tadaomi around.
Healing Factor: Koro-Sensei, amongst other abilities, has the power of regeneration. Even if he gets hit with the Applied Phlebotinum weapons, unless his body is almost completely destroyed, he'll recover in seconds.
Hidden Depths: Nagisa is heavily implied to be more than just the main perspective character, as evidenced by his training with Tadaomi in chapter 38. Tadaomi has the kids attempt to attack him with their anti-Koro-sense knives, which are harmless to humans. Suddenly, a monstrous snake attacks Tadaomi. This is later revealed to be some sort of hallucination he had, and it was actually Nagisa. Later, when Takaoka challenges the class to fight him with real knives (believing that, like his other recruits, they'll choke because they've never used a real weapon), Tadaomi gives the knife to Nagisa.
Hiroshima as a Unit of Measure: Every few chapters Koro-sensei is given a character introduction that includes one of these comparing to his ability to travel at mach 20. Some are fairly sensible (651.241 times Usain Bolt's 100 meter dash speed) while others are ridiculous (133,333.33 times faster than the speed of falling sakura petals).
Honey Pot: One of Irina's favorite tactics before she came to Class E.
Possibly intended as a reminder that there is a deadline for how long the students have left to kill Koro-Sensei.
Idiot Ball: The principal. Suffice to say. beating down the confidence of the only people in a legitimate position to end a world ending threat that will destroy ALL LIFE on the planet within a year is a terrible idea. If they fail due to, say a lack of confidence in their own abilities thanks to a systematic destruction, then he's equally culpable for the destruction of the human race in order to preserve his ideals as a teacher which favors grades over individuals. Worse, if they succeed? Then a phenomenally rich, highest quality assassin who has the favor of every government on the planet, the assistance of several of the worlds best assassins and an overtly obvious reason to HATE the principal for making their junior highschool years a living hell, has every reason to ruin/kill him with every resource available to them and basically no one to tell them not to. I mean... anyone with real authority knows they saved the world, right?
I'll Kill You!: Koro-sensei threatens to kill the families of class E if any of them endanger one another during an assassination attempt, and to kill the entire class if they don't pass a test with flying colors. The latter turned out to be a bluff, and probably the former too.
Informed Flaw: Class E is supposedly composed of the high school's worst students, but plenty of them seem reasonably intelligent.
In later chapters, it's revealed that they're the lower 1/5 of a school that is one of the prestigious in the country. Their Class E status is not due to their being unintelligent, but having lower test scores than the remaining 80% of the school (smart enough to meet the minimum requirements to enter the school, but not enough to excel).
Moreover, some of the students are extremely skilled in some subjects, but very weak in others (one student is very skilled in both math and science, but has failing grades in Japanese (the equivalent of western English classes)). Then, there's students like Karma, who were placed in class E as a disciplinary action.
Insane Troll Logic: The Chairman of the school is more interested in preserving his system than keeping Koro-sensei from destroying the world.
It's in the genes: he's son's got it, too. Of course the easiest way to beat your dad in your little info war is... an extended examination beat-down contest with Class E to force them to tell you what he's hiding? Huh? Why not just ask nicely?
Invisible Parents: Though they may be briefly mentioned on occasion, not a single parent of any student has ever appeared.
Japanese Ranguage: Invoked by Irina, who as the languuage teacher spends an entire lesson trying to get the students to avert this.
Jerk Ass: EVERYONE who isn't in Class-E, and several students who are. The school's chairman gets special mention, because he specially designed the school to encourage its students and teachers to be this way to everyone associated with Class E. Seriously, if this weren't a manga, a good half of this school's faculty would have been canned long ago in any country with a reasonable education system.
Koro-sensei, who will destroy the world, but also ensure that his students get good grades and become successful.
Karma, who is initially introduced as an Axe Crazy lunatic, but is later revealed to have been a Bully Hunter and an excellent student. What landed him in Class-E wasn't his being evil, but siding with a Class-E student who was being bullied.
Irina. She initially doesn't care about the students or believe in them, but she grows to care for them and increasingly become disgusted by the school's system of degrading Class-E.
Laser-Guided Karma: Whenever the higher-ranked students are shown to look down upon or make fun off Class-E students, Koro-sensei helps them to get their revenge or something eventually happens to make them regret it, unless the Chairman appears to intervene.
Marshmallow Hell: Irina tries to extract information on Koro-sensei's weaknesses by smothering him with her breasts. A couple non-class-E students find themselves incredibly jealous of him.
Messianic Archetype: For a creature who intends to destroy the world, Koro-sensei is an expert in making people change their ways for the better. Karma, Irina and "Red Eye" are all examples of this charisma and wisdom Koro-sensei possesses, along with his interactions with all of Class-E. He might as well be Buddha. Considering what Asano said about Koro-sensei "intending to become the world's savior", perhaps there is cause to this.
Mysterious Past: Koro-sensei. Why did he choose to become teacher of Class-E? Who is the woman to whom he made that promise? Where did he come from? What is he? These are just the first questions that come to mind.
When the Chairman takes the time to see him personally, he drops a HUGE hint: he says that Koro-Sensei was created to save the world, but wound up becoming its greatest threat.
Karasuma makes mention of another one: at one point in the past, Koro-sensei only had two legs and two arms. This was not the case in the flashback with the woman he made his promise to. In short, Koro-sensei might have once been Human.
On the other hand the students conclude that both Koro-sensei and Itona are artificial beings, with Itona being made after Koro-sensei.
Never Recycle Your Schemes: Justified. Once Koro-sensei knows how to defeat a tactic, he's smart enough and aware enough that it will never have a chance of working on him again.
Nice Guy: Tadaomi, the government agent assigned to overlook the class and help sharpen their assassination skills, only wants to save the world while ensuring that the kids are both safe and successful in their classes. He generally keeps calm about it, but is not pleased with the Chairman's school system.
No Export for You: Editors for the American version of Weekly Shonen Jump have stated in their podcast that, despite its popularity in Japan, the series will likely never be released Stateside due to the subject matter of high school students trying to kill their teacher.
Non-Standard Character Design: Koro-sensei and the Chairman both look quite distinct from any other character. Most characters are your basic anime designs, drawn with rounded lines and uneven hair. It goes without saying that Koro-sensei, being a tentacle monster, has a unique entirely rounded appearance. The Chairman is more subtly strange, but his design also feels off compared to (other) humans. He is incredibly angular and sharp-looking, and his clothes have noticeably fewer creases and wrinkles. The contrast between the two is probably intentional, to match their opposing roles in the story.
Not So Stoic: Takaoka's Dissonant Serenity is shattered in chapter 41 courtesy of Nagisa. His grinning gives way to shock, then mind-numbing fear, and finally frothing rage.
Not the Fall That Kills You: Averted, though it involves sudden acceleration rather than deceleration. Koro-sensei cannot accelerate as quickly as he normally would if he has to catch or carry a normal human being because their bodies couldn't handle the physical stress.
The Promise: Koro-Sensei is teaching the students in his class as a promise he made to someone. As he once put it, teaching all of his students seriously is much more important to him than the end of the world.
Pun: Tons. Of particular note, Koro-sensei's name was chosen for him by the class for sounding similar to "korosenai," the potential-negative form of the verb meaning "to kill," so it means "cannot kill" or "cannot be killed."
Reasonable Authority Figure: Tadaomi, who cares just as much for making sure the Class E students can overcome the chairman's system as he does keeping them healthy and safe while making sure they can stop Koro-sense from destroying the world.
Koro-sensei doesn't seem like this at first, but is soon revealed to be one.
The Rival: Takaoka was this to Tadaomi in training.
Sadist Teacher: Takaoka Akira. He's more akin to a drill sergeant than a teacher, instituting a ten period class schedule, most of which consists entirely of training, and isn't above smacking any disagreeable student (girls included) around.
Save Our Students: Koro-sensei is at Kunugigaoka Middle School to help their lowest-performing students excel... through a liberal application of super powers and some rather unusual extracurricular activities. Avoids Glurge by making his successes not a matter of whether he cares or not, but due to the fact that he is just an inhumanly good teacher.
Scare 'Em Straight: Parodied. Koro-sensei draws a short comic that is presented as if it were this to Megu to warn her that she may grow up to be dangerously codependent if she does not learn to stand up for her own needs more. It's much funnier in the manga than how it is described here.
When wearing a headband for each student showing their weak subjects, he wears a Naruto Headband for a student that's bad in many.
When Irina starts teaching the kids how to speak in foreign languages, basing her lessons around her experience in seducing foreigners, a female student pictures Jack Sparrow and another student pictures Lara Croft.
Super Speed: Koro-Sensei, as previously mentioned, can move at Mach 20. He eats shaved ice he personally gathers from the North Pole. He eats Chinese food on his lunch break...in China.
Supporting Protagonist: Nagisa. From chapter 1 onward, he's been making note of every weakness his sensei has, from the weak, like Sensei's preference for large breasts, to the strong, like his reduced stamina after regenerating a wound, and his inability to swim.
Koro-sensei: ...I mean, I just don't really feel like swimming. And it's not like my tentacles get all bloated underwater and I can't move or anything.
Synthetic Plague: Class E gets infected by one at the end of chapter 60. Early symptoms differ between people, so some of them are still on their feet while others are vomiting blood. All of a sudden, things just got extremely real.
Itona: I...am victorious. I have proven myself to be stronger than this classroom's walls.
This Was His True Form: It hasn't happened yet, but in Chapter 32 there's a panel that implies this will happen to Korosensei when he is killed.
Two Lines, No Waiting: The main plot line of training and attempting to assassinate Koro-sensei is interwoven with the students dealing with various problems in their school lives.
Tykebomb: A young boy who has powers similar to Koro-sensei transfers into the class in order to kill Koro-sensei. His handler also follows him in because he's rather Axe Crazy.
The Unreveal: After fighting Itona Koro-sensei decides he has no choice but to reveal a shocking truth about himself. He is actually an artificially created creature.
Entire class: Well, duh. And?
Wake Up, Go to School, Save the World: Inverted. The story is set up like this, but while the students' social and academic lives are challenging, they're trivial compared to the task of killing Koro-sensei.
Weak, but Skilled: Akira notes that Nagisa is amongst the weakest of the boys, with physical stats closer to that of a girl's. A few pages later, Karasuma is staring at Nagisa in awe as he managed to take down Akira in a matter of seconds and noting that Nagisa's talent never would have been discovered in the course of a normal school life.
We Need a Distraction: When it seems like Koro-sensei is about to discover Megu's plan to assassinate him in the water, Nagisa steps in to take advantage of his weaknesses ("he's very worried about appearances") by taunting him about some fan-letters to a big-breasted actress he found on Koro-sensei's desk.
Would Hurt a Child: Akira is not above hurting disobedient students. The chairman is an emotional variant of this.
Worthy Opponent: Shindou considers Sugino one, to the point of warning him of Class A's antics.
You Gotta Have Blue Hair: Nagisa, though he and Kaede are pretty much the only ones with unusual hair. Everyone else has normal colors.
Your Size May Vary: Used artistically, particularly with Nagisa and Takaoka to emphasize the David Vs Goliath aspect of their fight. Sometimes they would be drawn close to their actual relative proportions, sometimes Takaoka would look twice as tall as Nagisa.