Episode 3 opens with a new style of physical education and a new student. Karasuma is using physical education to properly teach the students the basics of assassination such as knife-wielding. The students seem to enjoy Karasuma’s presence and think he is cool which makes Koro-sensei jealous that the affection of his students is being stolen away.
The new student, Karma Akabane (wow his name is dumb), shows up and it is revealed that he knew Nagisa from their first and second year classes. Karma approaches Koro-sensei as a charming and polite student. This is, of course, revealed to be a façade as he shakes Koro-sensei’s tentacle, destroying part of it with knife pieces taped to his own hand. Karma is the first student to injure Koro-sensei and does so more than once in this episode with his cunning.
After the first injury, Koro is angered at being called a pushover and sulks, punching the wall and disturbing his students while they are taking an exam. Karma, who has already finished his test, reveals that he has stolen Koro-sensei’s Italian gelato and provokes the teacher. As Koro-sensei approaches, he steps into a minefield of the BBs that injure him again.
Karma is revealed to be cunning and highly intelligent. He is only in E class for his violent outbursts. He even threatens some regular students for making fun of Nagisa. He and Nagisa then go on a walk and he discovers that Koro-sensei doesn’t mind being called an octopus. He also discovers, much to his delight, that Koro-sensei is a real teacher in nature. Karma is delighted that he gets to kill a teacher, stating that the last one “up and died” on him.
Now, before anyone gets any misconceptions, no teachers were killed in this episode. Nor did any teachers just die. Karma’s last teacher provided him with support until Karma injured one of the star pupils at the school. If said pupil’s grades struggled, the teacher would be the one who came under criticism for such a thing. Thus, Karma’s old teacher had him transferred to E class following Karma’s suspension. Karma now considers his old teacher dead to him and thus proves that he is a strangely twisted youth.
Koro is, at the beginning of the episode, at a loss for how to deal with Karma. However, when Karma leaves an octopus skewered to the desk, stating he mistook it for Koro, Koro-sensei makes the student takoyaki at mach 20 speeds! Koro reveals that he is determined to polish Karma’s mind and body each time the student attempts to kill him. Throughout the episode, Koro disarms Karma of a gun and does nail art on him and also places Karma in a frilly pink apron for trying to kill him during home-ec class. Koro even styles Karma’s hair, further confusing the poor youth.
As a last ditch effort, Karma leads Koro outside, inquiring whether or not he is willing to risk his life for his students. And of course, Koro-sensei is! Karma jumps backwards off of the cliff behind him, holding a gun out. If Koro jumps after him, Karma will shoot him and they will both die. Koro miraculously saves Karma by making his body into a sticky web/net to catch Karma. He tells Karma that he won’t let him die.
Karma gives up, for the time being stating that – “He won’t die and he can’t be killed…at least not the teacher side of him.”