Nozomu notices a few members of the class playing a "spot the differences" game. Nozomu tells them that it is important to spot mistakes and he instructs the class in how life is filled with mistakes. He asks the class to identify mistakes in their lives after pointing out several of his own. After Nozomu contradicts himself, saying that a mistake was the correct action, Kafuka reasons that if a mistake comes to light, it is correct, resulting in many people approaching her, confessing their mistakes, making them correct. In the end of the first part, a boy approaches Nozomu, calling him "Dad." The second part of the episode reveals that he is actually Nozomu's brother's child, Majiru. Nozomu asks him to prove that he is indeed his nephew, and then asks all of his students to prove that they are the real one. When Majiru asks Nozomu to prove he is genuine, Nozomu is unable to come up with a response, and runs off. The episode ends with a sequence that deals with Majiru's hair fetish.

Harumi Fujiyoshi is listening to a Zetsubō Sensei radio show at home while working on her yaoi dōjinshi. The radio show is actually derived from a chapter of the Zetsubō Sensei manga, which portrays Japanese people's indifference to their ages and introduces a new character, Manami Ōkusa, who is a married high school student. In the second part of the episode, Nozomu criticizes the society where individuals are compelled to serve their 'duties' to meet other people's expectations. These 'duties' are often very superfluous and trivial. However, Kafuka points out the irony that Nozomu himself is a part of such a society, as the girls around him are expected to serve their various 'duties' to take care of their teacher. In the third part of the episode, Nozomu is in despair about society, where serious matters are often taken too lightly. Several of Nozumu's students provide their experiences of such a trend. After Rin Itoshiki makes an appearance as one of Nozomu's new students, Nozomu and his students decide to reverse the trend by treating various trivial matters with serious attitudes, which eventually becomes an addicting habit for everyone.

Nozomu Itoshiki watches a live baseball game and is reminded of a fact that many baseball stadiums intentionally reduce the flight range of baseball to make the game more enjoyable to watch. He suddenly realizes that such practices of intentional 'detuning' are quite popular in Japanese society. Nozomu points out that some people use 'detuning' as an excuse for their faults, Kafuka explains that people in general feels more comfortable with 'detuned' products rather than the cutting-edge one. In the second part of the episode, Nozomu states that there is an increasing tendency of saying 'not bad, not bad' at terrible things to comfort the victims. However, Nozomu explains that such instance can turn out to be a 'mini-propaganda', which could unknowingly mislead other people to believe in the same way. In the third part of the episode, Nozomu refuses to teach the first period class, because he was previously rejected by a restaurant in Kyoto as he was a first-time customer. He realzies that the Sayonara Zetsubō Sensei anime series could have been difficult series to approach for the first-time audience, so he decides to start the first-time-friendly episode. However, he is annoyed by the constant inquries from the first-time audiences. Thus, he decides to only invite regular audiences, but they seem to knows too much about the series. Ultimately, he decides to also reject the regular audience from the show.

It's Valentine's Day and Kagerou is afraid to open his box, because he doesn't really know whether any girl had dedicated a love letter to him or had not. Nozomu tells hit not to open it, in order to create a Schrodinger's box, in which the possibilities of the presence of any letter and the possibilities of absence are both infinite. A missile drops on the school's field and the class tries despairingly to hide it. An interviewer is, in fact, going to come to the school. After purchasing all the houses and getting the ramen shop Rin notices how the flavour has changed because of changing of her new management.