History Fridge / AssassinationClassroom

* The three main human characters of Assassination Classroom, Nagisa, Kayano and Karma all have several things in common if you notice. The first would be that they all have pretty unnatural hair colors, Nagisa's being blue, Kayano's being green and Karma's being bright red, though Kayano's hair is dyed. Another is that there is something weird about their names; Nagisa was named specifically so his mother could think of him as a girl, Karma's name is pretty weird on it's own (though he states he likes his name and asks to be called it over his surname), and Kayano's name isn't even real, her name is actually Akari Yukimura. The last similarity is that all three have attempted to kill Korosensei in a way that basically doubled as suicide; one of Nagisa's first attempts was by wearing a small grenade while hugging Korosensei that would have killed him if not for Korosensei's intervention. Karma explicitly stated that his XanatosGambit would end with either both him and Korosensei dead, as he would shoot Korosensei as the teacher tried to save him from jumping off a cliff. Or Korosensei would 'die' as a teacher for letting Karma kill himself. However, thanks to Korosensei's quick thinking, neither ended up dead. In Kayano's second assassination attempt, she used tentacles she implanted in her neck that very obviously harming her body. Itona even stated that she would have only survived about a minute or so like that. Luckily, Nagisa managed to save her via kissing.

* The students sure seem to like shaking their hands around during season one's openings. But that's not all; if you take a closer look at their hands, they form two gestures: a closed hand moving back and forth (as if holding a knife and stabbing someone), and an open hand (a gesture used for calling a teacher's attention to either ask a question or to answer). It is a neat symbolism of their relationship with Koro-sensei, who is their target AND their teacher.

* Some of Koro-sensei's weaknesses can be inferred or justified by his personality, actions, or another weakness.

** '''Weakness 29: He gets carried away by official positions''', where he took his role as the jailer during the Cops and Robbers game way too seriously. Earlier, Koro-sensei also played the role of a hot-blooded baseball coach and an overly strict lifeguard ('''Weakness 22: He’s very strict about poolside manner''') to the same degree. But what's Koro-sensei's official job, you know, the one that he's ''really'' good at and the primary motivation behind playing all of the above positions so well? [[Heartwarming/AssassinationClassroom Being Class-E's homeroom teacher]].
* The amount of weaknesses Koro-sensei has and how he can't truly overcome them? Makes complete sense once his backstory is out and it's revealed that, contrary to Itona's request to be strong, he asked to be ''weak''.

** His affinity for mimicking or impersonating people from pop culture isn’t just for laughs—given that Human!Korosensei had little to no interest in anything but his job, he’s probably learned everything he has about the world since from reading manga and watching movies/TV.

* In chapter 133, Korosensei starts revealing his back-story by stating that he was once an assassin known as the "God of Death" two years ago. All of a sudden, all of the advice he gives and all of the lessons he taught to his students about assassination makes sense - he was once [[WorldsBestWarrior THE Best Assassin In the World,]], so of course he'd be the best teacher for a class about assassinations, particularly his own.

* Back on the page for UsefulNotes/The47Ronin, it mentions that a lot of the characters in ''Assassination Classroom'' are named after them, with Korosensei being an analogue to Kira. the oft mentioned question of the possibility of Kira dying of natural causes before the actual assassination happens is finally given an analogue through the simple fact that Koro-sensei could [[SecretlyDying eventually meet his end in such a fashion]] if the students don't kill him themselves by March, with the rest of the world hanging in the balance as well.
* The bit of EarlyInstallmentWeirdness where Korosensei actually threatened everyone's ''families'' to hammer home how serious is about how they cannot endanger each other in their mission? Considering his mannerisms are based off of Yukimura Aguri and this is early in on the year, he hasn't fully embraced his new persona. And, on top of that, having someone nearly get killed while ''hugging'' him would strongly remind him of Aguri's death.

* Re-reading the series, it seems like Korosensei in the early chapters acts wildly [[OutOfCharacter out of character]] -- he’s cocky, bratty, and sometimes selfish, and he threatens his students in ways that his later self would never do. While some of this can be chalked up to EarlyInstallmentWeirdness, it actually shows how much Korosensei grows up alongside the students: Much like Irina, Korosensei has no idea how to be a normal person, and on an emotional level, he’s just a child using a murderer’s tactics to educate teenagers. As the story progresses, however, his ego is deflated, he learns to control his emotional outbursts, and whatever selfish impulses he had are wiped out by his care and dedication to his students. He also moves away from using brutal or violent means to make a point (a common tactic for people whose usual methods aren’t working), and instead switches to lightheartedness, positive reinforcement, and occasionally subtle manipulation—all tactics used by teachers to bring out the best in their students.
* No wonder Korosensei was so angry when Itone revealed his tentacles -- after going through a similar experience, Korosensei knows how horrifically painful the procedure is, and he must have realized that the government gave the same excruciating treatment ''[[WouldHurtAChild to a child]]''.
* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the ''[[{{Determinator}} most motivated characters]]'' ever?

*** ...or sacrifice herself in order to kill Korosensei.

** Behold chapter 173.

* Speaking of weaknesses - quite a few of Korosensei’s biggest flaws and bad habits at the beginning of the series make sense once you know his backstory:

* In Kayano's spotlight chapter, she builds a giant, bomb-concealing pudding for the purpose of killing Korosensei. The other students help her, and [[FriendshipMoment a good time is had by all]]. Finally, just Korosensei is about to eat the finished pudding, Kayano ''flips out''- she has so many good memories associated with that pudding that [[{{Foreshadowing}} she can't bear to see it destroyed]]. The same thing happens dozens of chapters later with her 'false' persona, which was created for the same reason.

* Which student was it who ultimately "killed" the threat that Koro-sensei was for the Earth? It was Okuda, who politely ASKED for her teacher's help in her attempt to do so. Of course Korosensei would make sure that was the best assassination ever. And the Anti-Matter was destroyed.

* Which student was it who ultimately "killed" the threat that Koro-sensei was for the Earth? It was Okuda, who politely ASKED for her teacher's help in her attempt to do so. Of course Koro-sensei would make sure that was the best assassination ever. And the Anti-Matter was destroyed.
* The fact that Koro-sensei had the students kill him instead of the laser. As all the suspicion being placed upon them would quickly disperse. Since they killed the "monster" who allegedly brainwashed them causing them to be viewed as heroes.
* Nagisa in the final has not grown an inch since middle school, his parents never got back together, and is placed in a, possibly dangerous, classroom full of delinquents. He still makes it work, which works perfectly for the biggest character and ultimately the protagonist of the series. No, he didn't get exactly what he wanted, but he can keep going anyways and manage to succeed...something that is a good thing to show to the readers.

* In chapter 95, Korosensei snaps and slaps his students because their reckless and arrogant use of their athletic abilities made them injure an old man; Korosensei specifically accuses them of forgetting to "think from the standpoint of the weak". In chapter 140, we learn why that event enraged him so much: that flawed mindset is exactly why he couldn't prevent [[MyGreatestFailure Aguri's death]]. In his life, he only cared about gaining "strong" abilities - those that could be used to kill others; he lacked any ability that could've been used to help the "weak", like the medical knowledge to heal Aguri's wound. During his rampage, he was completely focused on the "strong" enemies, so he ignored the "weak" Aguri and failed to protect her from the tentacle mine, causing her to get get that fatal injury.
* Nagisa learns the "stun clap" technique (clapping when the opponent is highly stressed, to distract them for a critical instant or even to paralyze them), and initially wants to be an assassin. Later on, he develops a "calming touch" technique (touching someone in the neck when the're highly stressed, to distract them and snap them out of their panic) to calm down Sakura, and that event is what makes him decide to become a teacher instead. Both of these techniques are based on a similar principle. In the manga, the first chronological usage of these techniques is the original God of Death - an assassin - knocking out Yanagisawa by hitting a glass pane; the last is Korosensei - the original God of Death turned into a teacher - calming down Nagisa.

* The three main human characters of Assassination Classroom, Nagisa, Kayano and Karma all have several things in common if you notice. The first would be that they all have pretty unnatural hair colours, Nagisa's being blue, Kayano's being green and Karma's being bright red, though Kayano's hair is dyed. Another is that there is something weird about their names; Nagisa was named specifically so his mother could think of him as a girl, Karma's name is pretty weird on it's own (though he states he likes his name and asks to be called it over his surname), and Kayano's name isn't even real, her name is actually Akari Yukimura. The last similarity is that all three have attempted to kill Korosensei in a way that basically doubled as suicide; one of Nagisa's first attempts was by wearing a small grenade while hugging Korosensei that would have killed him if not for Korosensei's intervention. Karma explicitly stated that his XanatosGambit would end with either both him and Korosensei dead, as he would shoot Korosensei as the teacher tried to save him from jumping off a cliff. Or Korosensei would 'die' as a teacher for letting Karma kill himself. However, thanks to Korosensei's quick thinking, neither ended up dead. In Kayano's second assassination attempt, she used tentacles she implanted in her neck that very obviously harming her body. Itona even stated that she would have only survived about a minute or so like that. Luckily, Nagisa managed to save her via kissing.

* Re-reading the series, it seems like Korosensei in the early chapters acts wildly [[OutOfCharacter out of character]]—he’s cocky, bratty, and sometimes selfish, and he threatens his students in ways that his later self would never do. While some of this can be chalked up to EarlyInstallmentWeirdness, it actually shows how much Korosensei grows up alongside the students: Much like Irina, Korosensei has no idea how to be a normal person, and on an emotional level, he’s just a child using a murderer’s tactics to educate teenagers. As the story progresses, however, his ego is deflated, he learns to control his emotional outbursts, and whatever selfish impulses he had are wiped out by his care and dedication to his students. He also moves away from using brutal or violent means to make a point (a common tactic for people whose usual methods aren’t working), and instead switches to lightheartedness, positive reinforcement, and occasionally subtle manipulation—all tactics used by teachers to bring out the best in their students.
* No wonder Korosensei was so angry when Itone revealed his tentacles—after going through a similar experience, Korosensei knows how horrifically painful the procedure is, and he must have realized that the government gave the same excruciating treatment ''[[WouldHurtAChild to a child]]''.
* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the ''[[{{Determinator}} most motivated characters]]''ever?

* During the intro to the Hotel Arc, the mastermind demands that Nagisa and Kayano trade off Koro-sensei for the antidote. Karasuma considers complying, despite the risk of a worst case scenario where both kids are kidnapped and the antidote is never handed over, but eventually decides against it. After reading the entirety of the arc, you'll realize just how ''horrific'' the actual "worst case scenario" would've turned out:
** As detailed during TheReveal, Kayano and Koro-sensei would have been restrained and buried together in anti-sensei material and cement. Koro-sensei could either escape by exploding, killing Kayano in the process, or save her life by sacrificing himself and succumbing to the anti-material. Though there's no guarantee that the second option would've been explosion free...
** Meanwhile, the same events would've occurred for Nagisa: Takaoka would have trapped him on the heliport and blown up the antidote, sending Nagisa spiraling into his UnstoppableRage--except Terasaka wouldn't have been there to throw him the stun gun and snap him out of his bloodlust. Without a clear head and the second weapon, Nagisa would not have been able to utilize the secret technique, rendering him powerless to stop Takaoka from killing him. Or, to take Takaoka's words at their horrifying face value, from killing him ''[[ColdBloodedTorture very, very slowly]]''.

*** ...or sacrifice herself in order to kill Koro-sensei.

* Koro-sensei's backstory reveals he asked to be ''weak'' during his transformation. This guy who can go Mach 20 and is nigh unkillable is ''weak''. The amount of power one might have if they went through the same process and asked for strength is horrifying with that in mind.
** Itona Horibe and Akari Yukimira desired strength and both went crazy with their new powers as a result of the tentacles absorbing a ton of energy from the brain in order to grant them this power. If Koro-sensei asked for the same thing, he would have been an insane monster hellbent on killing everyone on the planet.

* Yanagisawa/Shiro has repeatedly declared his intention to give Koro-sensei "the cruelest death imaginable." In Chapter 170, he and the second God of Death show up, interrupting a heartwarming moment between Koro-sensei and his students and revealing that "Number 2" has been transformed into another tentacle monster. Past assassins, including Number 2, have noted that using Koro-sensei's concern for his students against him is an extremely effective tactic. Now, under those circumstances, what could possibly be the cruelest thing to do to Koro-sensei...?

* It could be chalked up to EarlyInstallmentWeirdness, but late in the story Koro-sensei reveals that his tentacles make him ''fast'' but not correspondingly ''strong'', and in terms of his actual strength he isn't that much stronger than a human being. Except in early arcs he was shown casually handling anti-air missiles, even holding one in place perfectly when its rocket fired, without any apparent effort. That would require a ''tremendous'' amount of strength. One has to wonder if he made up that weakness entirely.

** Okay, but what about holding it in place while its rocket is firing? Presumably those missiles' rockets are powerful enough to shift something of Koro-sensei's weight.
*** Again, not really. Koro-sensei said it had been shot at him, which means most of the fuel has already been used up. What little was left wouldn't be too powerful; it'd be enough to ignite, but that'd be about it.

[[AC:FridgeBrilliance]]

[[AC:FridgeHorror]]

[[AC:FridgeLogic]]

*** Again, not really. Koro-sensei said it had been shot at him, which means most of the fuel has already been used up. What little was left wouldn't be too powerful; it'd be enough to ignite, but that'd be about it.

** '''Weakness 12: Getting wet'''. During a particularly humid day, his head absorbed the moisture in the air and swelled up. [[spoiler: A later chapter reveals '''Weakness 23: He can’t swim'''. His entire body will swell up when exposed to water]].

* The amount of weaknesses Koro-sensei has and how he can't truly overcome them? [[spoiler: Makes complete sense once his backstory is out and it's revealed that, contrary to Itona's request to be strong, he asked to be ''weak''.]]

* Nagisa is always wearing two thin, black bracelets around his wrists. [[spoiler: After Chapter 112's reveal, it's safe to assume that they're actually back up hair ties. He ''really'' doesn't want to be seen in public with his long hair down.]]

* The Chapter 125 Colour Page has Kayano and Koro-sensei on it for Valentine's Day, both of them thinking about the same type of candy in the snow, and a Valentine's candy box with "Got to '''kill''' soon" written on it, with the "kill" written over "meet". Then along came chapter 128: [[spoiler:[[WhamEpisode Kayano has tentacles and wants to kill him.]]]] In hindsight, it was like a knife to the reader's throat and we never caught on until TheReveal blew it wide open, like a true assassination - we never saw it coming until it already occurred.
* Starting from Episode 7, when the class leaves for the Kyoto field trip, Ritsu appears at the end of the opening theme even though she isn't seen or formally introduced until Episode 9. It only makes sense when you realize that she did in fact made her classroom debut during Episode 7. [[spoiler: She was being installed there while the students were away on the field trip.]]
* In chapter 133, Korosensei starts revealing his back-story by stating that [[spoiler:he was once an assassin known as the "God of Death" two years ago.]] All of a sudden, all of the advice he gives and all of the lessons he taught to his students about assassination makes sense - [[spoiler:he was once [[WorldsBestWarrior THE Best Assassin In the World,]]]], so of course he'd be the best teacher for a class about assassinations, particularly his own.
** It also goes a long way to explain why, in the lead up to the God of Death arc, the initial victims were OnlyMostlyDead. The one who attacked them was [[spoiler:a skilled but significantly less competent copycat or inferior successor]].

* Ever since reading the title, I was really curious. It was revealed since the first chapter they were trained to kill the teacher, but isn't an assassin would be more suited to teach about assassination? Then Bitch-sensei came, and I am a bit disappointed after her introduction. And then there's the reveal in chapter 133. [[spoiler: It really IS an Assassination Classroom, where the children are taught to kill by the best assassin himself.]]
** Even better, with Irina they finally have teachers covering all facets of assassination. Karasuma works their physical abilities while Irina, one of the best HoneyTrap style assassins in the world, trains their social skills so that they can manipulate people and get close to their target. [[spoiler: Korosensei's true strength as the God of Death was that he was a MasterOfAll polymath. Fittingly for their form teacher, he hones their mental skills and improvisational ability. His lessons often involve playing on their strengths and thinking their way through the assassination.]] Really, it is as good a class for raising assassins as anyone could ask for.
* Back on the page for UsefulNotes/The47Ronin, it mentions that a lot of the characters in ''Assassination Classroom'' are named after them, with Korosensei being an analogue to Kira. the oft mentioned question of [[spoiler: the possibility of Kira dying of natural causes before the actual assassination happens]] is finally given an analogue through the simple fact that [[spoiler: Koro-sensei could [[SecretlyDying eventually meet his end in such a fashion]] if the students don't kill him themselves by March, with the rest of the world hanging in the balance as well]].
* The bit of EarlyInstallmentWeirdness where Korosensei actually threatened everyone's ''families'' to hammer home how serious is about how they cannot endanger each other in their mission? [[spoiler: Considering his mannerisms are based off of Yukimura Aguri and this is early in on the year, he hasn't fully embraced his new persona. And, on top of that, having someone nearly get killed while ''hugging'' him would strongly remind him of Aguri's death.]]
* In Kayano's spotlight chapter, she builds a giant, bomb-concealing pudding for the purpose of killing Korosensei. The other students help her, and [[FriendshipMoment a good time is had by all]]. Finally, just Korosensei is about to eat the finished pudding, Kayano ''flips out''- she has so many good memories associated with that pudding that [[{{Foreshadowing}} she can't bear to see it destroyed]]. [[spoiler:The same thing happens dozens of chapters later with her 'false' persona, which was created for the same reason.]]
* FemmeFatale Irina is (somewhat) religious, making her a ''literal'' [[spoiler:praying mantis]].
* Which student was it who ultimately "killed" the threat that Koro-sensei was for the Earth? It was [[spoiler: Okuda, who politely ASKED for her teacher's help in her attempt to do so. Of course Koro-sensei would make sure that was the best assassination ever. And the Anti-Matter was destroyed.]]
* The fact that Koro-sensei had the students [[spoiler:kill him instead of the laser. As all the suspicion being placed upon them would quickly disperse. Since they killed the "monster" who allegedly brainwashed them causing them to be viewed as heroes.]]
* Nagisa in the final [[spoiler: has not grown an inch since middle school, his parents never got back together, and is placed in a, possibly dangerous, classroom full of delinquents.]] He still makes it work, which works perfectly for the biggest character and ultimately the protagonist of the series. No, he didn't get exactly what he wanted, but he can keep going anyways and manage to succeed...something that is a good thing to show to the readers.
* Kayano's obsession with big boobs? [[spoiler: It's probably a symptom of the tentacles, as both Korosensei and Itona were shown obsessing about big boobs.]]
* Korosensei's "as a fellow ikemen" comments during the arc about Isogai's part-time job are kinda out there and played for laughs. [[spoiler:As the old God of Death, he actually does fit the description of an ikemen rather well.]]
* A sad example that still impresses me with what a good character Nagisa is. In the earlier chapters, his skill at assassination just seemed like a cool ability for our protagonist. But once it's revealed that [[spoiler: his mother is deeply abusive, it's clear that his "superpower" is really his hypersensitivity towards people's emotions that he developed while trying to protect himself from his mother's anger.]] It really adds a layer of depth to the standard "the hero is just special", and makes his application of his ability by the end of the manga even more heartwarming.
* How come Kanzaki didn't get a haircut during the taboo game? She's either been taught to be really kind [[spoiler: by her really strict parents]] or it's because [[spoiler: of her experience as a gamer during her delinquent phase.]] Turns out she is that good at games.
* In chapter 95, Korosensei snaps and slaps his students because their reckless and arrogant use of their athletic abilities made them injure an old man; Korosensei specifically accuses them of forgetting to "think from the standpoint of the weak". In chapter 140, we learn why that event enraged him so much: [[spoiler:that flawed mindset is exactly why he couldn't prevent [[MyGreatestFailure Aguri's death]]. In his life, he only cared about gaining "strong" abilities - those that could be used to kill others; he lacked any ability that could've been used to help the "weak", like the medical knowledge to heal Aguri's wound. During his rampage, he was completely focused on the "strong" enemies, so he ignored the "weak" Aguri and failed to protect her from the tentacle mine, causing her to get get that fatal injury]].
* Nagisa learns the "stun clap" technique (clapping when the opponent is highly stressed, to distract them for a critical instant or even to paralyze them), and initially wants to be an assassin. Later on, he develops a "calming touch" technique (touching someone in the neck when the're highly stressed, to distract them and snap them out of their panic) to calm down Sakura, and that event is what makes him decide to become a teacher instead. Both of these techniques are based on a similar principle. In the manga, the first chronological usage of these techniques is [[spoiler:the original God of Death - an assassin - knocking out Yanagisawa by hitting a glass pane]]; the last is [[spoiler:Korosensei - the original God of Death turned into a teacher - calming down Nagisa]].
* Notice in chapter 149 [[spoiler:Nagisa didn't release Karma until Karasuma announced the surrender formally?]] In fact, Nagisa was still holding on with all his might, choking [[spoiler:Karma]] until he learned his side had won. This makes sense when you realize Karma is a dangerous BloodKnight who doubles as a bit of a ManipulativeBastard. Nagisa has seen Karma repeatedly beat people up and very rarely plays fair. During Karma's fight with Grip, he fights them evenly before faking being knocked out in order to finish off the assassin. Nagisa probably believed that that was what Karma was doing; trying to get Nagisa to release him so he could win. Nagisa, unlike the vast majority of Karma's opponents, has known him for a long time, and as such is used to Karma's tricks. There was no way he would take any chances until the surrender was for certain.
* The three main human characters of Assassination Classroom, Nagisa, Kayano and Karma all have several things in common if you notice. The first would be that they all have pretty unnatural hair colours, Nagisa's being blue, Kayano's being green and Karma's being bright red, though Kayano's hair is dyed. Another is that there is something weird about their names; Nagisa was [[spoiler:named specifically so his mother could think of him as a girl]], Karma's name is pretty weird on it's own (though he states he likes his name and asks to be called it over his surname), and Kayano's [[spoiler:name isn't even real, her name is actually Akari Yukimura]]. The last similarity is that all three have attempted to kill Korosensei in a way that basically doubled as suicide; one of Nagisa's first attempts was by wearing a small grenade while hugging Korosensei that would have killed him if not for Korosensei's intervention. Karma explicitly stated that his XanatosGambit would end with either both him and Korosensei dead, as he would shoot Korosensei as the teacher tried to save him from jumping off a cliff. Or Korosensei would 'die' as a teacher for letting Karma kill himself. However, thanks to Korosensei's quick thinking, neither ended up dead. In Kayano's second assassination attempt, she used [[spoiler: tentacles she implanted in her neck that very obviously harming her body. Itona even stated that she would have only survived about a minute or so like that]]. Luckily, Nagisa managed to save her via [[spoiler:kissing]].
* In the third opening of the anime, Question, you can see characters with certain relationships to each other shown side-by-side; Professor Bitch and Karasuma, and Principal Asano and Gakushuu. However, the Reaper appears all by his lonesome with what appears to be only his silhouette behind him. If you notice, this silhouette, though vaguely, resembles [[spoiler: Korosensei while he was human]], which would make sense, considering the nature of their relationship.

* Korosensei mentions in Chapter 30 that he wanted siblings, but his parents wouldn't go for it. Naturally, [[spoiler: living in a lawless warzone, they wouldn't risk raising another child in such a corrupt environment]].
* Korosensei's statistics page in Volume 1 states that his history is "agent of destruction/teacher." While obviously blowing up the moon would qualify him as the latter, his earlier profession as [[spoiler: an assassin]] would also fit this pretty well, making it ''very'' well-hidden foreshadowing.

* No wonder Korosensei was so angry when Itone revealed his tentacles—after [[spoiler: going through a similar experience]], Korosensei knows how horrifically painful the procedure is, and he must have realized that the government gave the same excruciating treatment ''[[WouldHurtAChild to a child]]''.
* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the ''[[Determinator most motivated characters]]''ever?

** As detailed during TheReveal, Kayano and Koro-sensei [[spoiler: would have been restrained and buried together in anti-sensei material and cement. Koro-sensei could either escape by exploding, killing Kayano in the process, or save her life by sacrificing himself and succumbing to the anti-material. Though there's no guarantee that the second option would've been explosion free...]]
** Meanwhile, the same events would've occurred for Nagisa: [[spoiler: Takaoka would have trapped him on the heliport and blown up the antidote, sending Nagisa spiraling into his UnstoppableRage--except Terasaka wouldn't have been there to throw him the stun gun and snap him out of his bloodlust. Without a clear head and the second weapon, Nagisa would not have been able to utilize the secret technique, rendering him powerless to stop Takaoka from killing him. Or, to take Takaoka's words at their horrifying face value, from killing him ''[[ColdBloodedTorture very, very slowly]]'']].
** To top it off, Nagisa [[spoiler: would never learn that the virus was a fake and his friends were never in any real danger. He would've died [[DespairEventHorizon thinking that his classmates were doomed to a slow, agonizing death]]]]. That would've been one HELL of a DownerEnding for this arc, if not for the entire series.
** With the reveal in Chapter 128, it can also be inferred that [[spoiler:The pool of anti-sensei material would have also killed Kayano anyways. Korosensei would have been in a situation where there was likely no chance to save Kayano, so he would have died knowing one of his students would have died with him.]]
** [[spoiler: Nah, Kayano won't surrender quietly, it's more likely she'd be forced to reveal identity and defeat Takaoka at that.]]
*** [[spoiler:...or sacrifice herself in order to kill Koro-sensei.]]

* Koro-sensei's backstory reveals he asked to be ''weak'' during his [[spoiler: transformation]]. This guy who can go Mach 20 and is nigh unkillable is ''weak''. The amount of power one might have if they went through the same process and asked for strength is horrifying with that in mind.
** Itona Horibe [[spoiler:and Akari Yukimira]] desired strength and both went crazy with their new powers as a result of the tentacles absorbing a ton of energy from the brain in order to grant them this power. If Koro-sensei asked for the same thing, he would have been an insane monster hellbent on killing everyone on the planet.
** And it seems like [[spoiler:the second Reaper]] has become just that as of [[spoiler:Chapter 157]].
* Yanagisawa/Shiro has repeatedly declared his intention to give Koro-sensei "the cruelest death imaginable." In Chapter 170, [[spoiler: he and the second God of Death show up, interrupting a heartwarming moment between Koro-sensei and his students and revealing that "Number 2" has been transformed into another tentacle monster. Past assassins, including Number 2, have noted that using Koro-sensei's concern for his students against him is an extremely effective tactic. Now, under those circumstances, what could possibly be the cruelest thing to do to Koro-sensei...?]]

* The Chairman's heart, while twisted, was in the right place by wanting his students to come out from his teachings stronger mentally and physically, thanks to his previous student's [[spoiler: [[DrivenToSuicide suicide]]]]. But with his emotionally exhausting teaching methods, his brainwashing, and his strictness, who's to say that somewhere down the line his students won't come out of there [[spoiler: suicidal]] as well?

* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the {{Determinator most motivated characters}} ever?

* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the {{Determinater most motivated characters}} ever?

* Korosensei's statistics page in Volume 1 states that his history is "agent of destruction/teacher." While obviously blowing up the moon would qualify him as the latter, his earlier profession as [[spoiler: an assassin]] would also fit this pretty well, making it ''very'' well-hidden forhadowing.

* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the [[Determinater most motivated characters]] ever?

* He's so horrible at following people unnoticed (and always so shocked when people see him) because he’s used to never being seen when he stalks people; though he uses the same techniques he always did as an assassin, he hasn’t yet grasped that his huge brightly-colored body makes it impossible for him to hide the same way he could when he was human.

* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the [[Determinator]] most motivated characters]] ever?

* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the [[Determinator most motivated characters ]] ever?

* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the [[Determinator most motivated characters]] ever?

** Okay, but what about holding it in place while its rocket is firing? Presumably those missiles' rockets are powerful enough to shift something of Koro-sensei's weight.

** Actually, not necessarily. Military-grade anti-air missiles are still relatively light; the one he was holding would only be about 22kg (or 48.5 pounds), possibly lighter if it was out of fuel or he'd already removed the warhead.

* Nagisa in the final [[spoiler: has not grown an inch since middle school, his parents never got back together, and is placed in a, possibly dangerous, classroom full of delinquents.]] He still makes it work, which works perfectly for the biggest character and ultimately TheProtagonist of the series. No, he didn't get exactly what he wanted, but he can keep going anyways and manage to succeed...something that is a good thing to show to the readers.
* Kayano's obsession with big boobs? [[spoiler: It's probably a symptom of the tentacles, as both Korosensei and Itona were shown obssesing about big boobs.]]

* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the {{Determinator most motivated characters}} ever?

* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a {{Franchise/Naruto}} headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a {{Shonen}} manga with one of the [[{{Determinator most motivated characters}}]] ever?

* In Chapter 12, Terasaka is the only one who has a Korosensei clone with a [[Franchise/Naruto]] headband. As Korosensei points out, Terasaka is weak in every subject except P.E., meaning he'll need to study even harder than the others to get a good grade point average. But at this point, Terasaka is unmotivated and doesn't want to put in the effort. Korosensei understands this, and his goal isn't to tutor Terasaka - first he has to motivate him. And what better way to encourage a listless student than to show them a [[Shonen]] manga with one of the [[Determinator most motivated characters]] ever?

* No wonder Korosensei was so angry when Itone revealed his tentacles—after [[spoiler: going through a similar experience]], Korosensei knows how horrifically painful the procedure is, and he must have realized that the government gave the same excruciating treatment [[WouldHurtAChild ''to a child'']].

** Even better, with Irina they finally have teachers covering all facets of assassination. Karasuma works their physical abilities while Irina, one of the best HoneyTrap style assassins in the world, trains their social skills so that they can manipulate people and get close to their target. [[spoiler: Koro-sensei's true strength as the God of Death was that he was a MasterOfAll polymath. Fittingly for their form teacher, he hones their mental skills and improvisational ability. His lessons often involve playing on their strengths and thinking their way through the assassination.]] Really, it is as good a class for raising assassins as anyone could ask for.
* Back on the page for UsefulNotes/The47Ronin, it mentions that a lot of the characters in ''Assassination Classroom'' are named after them, with Koro-sensei being an analogue to Kira. the oft mentioned question of [[spoiler: the possibility of Kira dying of natural causes before the actual assassination happens]] is finally given an analogue through the simple fact that [[spoiler: Koro-sensei could [[SecretlyDying eventually meet his end in such a fashion]] if the students don't kill him themselves by March, with the rest of the world hanging in the balance as well]].
* The bit of EarlyInstallmentWeirdness where Koro-sensei actually threatened everyone's ''families'' to hammer home how serious is about how they cannot endanger each other in their mission? [[spoiler: Considering his mannerisms are based off of Yukimura Aguri and this is early in on the year, he hasn't fully embraced his new persona. And, on top of that, having someone nearly get killed while ''hugging'' him would strongly remind him of Aguri's death.]]
* In Kayano's spotlight chapter, she builds a giant, bomb-concealing pudding for the purpose of killing Koro-sensei. The other students help her, and [[FriendshipMoment a good time is had by all]]. Finally, just Koro-sensei is about to eat the finished pudding, Kayano ''flips out''- she has so many good memories associated with that pudding that [[{{Foreshadowing}} she can't bear to see it destroyed]]. [[spoiler:The same thing happens dozens of chapters later with her 'false' persona, which was created for the same reason.]]

* Kayano's obsession with big boobs? [[spoiler: It's probably a symptome of the tentacles, as both Korosensei and Itona were shown obssesing about big boobs.]]

* In chapter 95, Korosensei snaps and slaps his students because their reckless and arrogant use of their athletic abilities made them injure an old man; Koro-sensei specifically accuses them of forgetting to "think from the standpoint of the weak". In chapter 140, we learn why that event enraged him so much: [[spoiler:that flawed mindset is exactly why he couldn't prevent [[MyGreatestFailure Aguri's death]]. In his life, he only cared about gaining "strong" abilities - those that could be used to kill others; he lacked any ability that could've been used to help the "weak", like the medical knowledge to heal Aguri's wound. During his rampage, he was completely focused on the "strong" enemies, so he ignored the "weak" Aguri and failed to protect her from the tentacle mine, causing her to get get that fatal injury]].

** He worries so much about his reputation because after his original unsavory life as a murderer, he’s really determined to be seen as an upstanding role model…[[SweetTooth even]] [[Pervert when he’s]] [[GossipyHens not]].

* Koro-sensei's "as a fellow ikemen" comments during the arc about Isogai's part-time job are kinda out there and played for laughs. [[spoiler:As the old God of Death, he actually does fit the description of an ikemen rather well.]]

* In chapter 95, Koro-sensei snaps and slaps his students because their reckless and arrogant use of their athletic abilities made them injure an old man; Koro-sensei specifically accuses them of forgetting to "think from the standpoint of the weak". In chapter 140, we learn why that event enraged him so much: [[spoiler:that flawed mindset is exactly why he couldn't prevent [[MyGreatestFailure Aguri's death]]. In his life, he only cared about gaining "strong" abilities - those that could be used to kill others; he lacked any ability that could've been used to help the "weak", like the medical knowledge to heal Aguri's wound. During his rampage, he was completely focused on the "strong" enemies, so he ignored the "weak" Aguri and failed to protect her from the tentacle mine, causing her to get get that fatal injury]].
* Nagisa learns the "stun clap" technique (clapping when the opponent is highly stressed, to distract them for a critical instant or even to paralyze them), and initially wants to be an assassin. Later on, he develops a "calming touch" technique (touching someone in the neck when the're highly stressed, to distract them and snap them out of their panic) to calm down Sakura, and that event is what makes him decide to become a teacher instead. Both of these techniques are based on a similar principle. In the manga, the first chronological usage of these techniques is [[spoiler:the original God of Death - an assassin - knocking out Yanagisawa by hitting a glass pane]]; the last is [[spoiler:Koro-sensei - the original God of Death turned into a teacher - calming down Nagisa]].

* In the third opening of the anime, Question, you can see characters with certain relationships to each other shown side-by-side; Professor Bitch and Karasuma, and Principal Asano and Gakushuu. However, the Reaper appears all by his lonesome with what appears to be only his silhouette behind him. If you notice, this silhouette, though vaguely, resembles [[spoiler:Korosensei while he was human]], which would make sense, considering the nature of their relationship.

* Re-reading the series, it seems like Korosensei in the early chapters acts wildly [[OutOfCharacter out of character]]—he’s cocky, bratty, and sometimes selfish, and he threatens his students in ways that his later self would never do. While some of this can be chalked up to [[Early Installment Weirdness]], it actually shows how much Korosensei grows up alongside the students: Much like Irina, Korosensei has no idea how to be a normal person, and on an emotional level, he’s just a child using a murderer’s tactics to educate teenagers. As the story progresses, however, his ego is deflated, he learns to control his emotional outbursts, and whatever selfish impulses he had are wiped out by his care and dedication to his students. He also moves away from using brutal or violent means to make a point (a common tactic for people whose usual methods aren’t working), and instead switches to lightheartedness, positive reinforcement, and occasionally subtle manipulation—all tactics used by teachers to bring out the best in their students.

* Korosensei's statistics page in Volume 1 states that his history is "agent of destruction/teacher." While obviously blowing up the moon would qualify him as the latter, his earlier profession as [[spoiler: an assassin]] would also fit this pretty well, making it ''very'' well-hidden ForShadowing.

* Korosensei's statistics page in Volume 1 states that his history is "agent of destruction/teacher." While obviously blowing up the moon would qualify him as the latter, his earlier profession as [[spoiler: an assassin]] would also fit this pretty well, making it ''very'' well-hidden Forshadowing.