Sayonara Zetsubou Sensei

Kafuka Fuura is cheerily walking to school one April morning when she suddenly spots a man trying to hang himself in a fit of despair. Kafuka manages to use her weight to snap the rope, thus saving his life. Nozomu Itoshiki, the man, eventually cannot take anymore of the girl's ridiculous ramblings, and runs off to school to start homeroom at the beginning of a new school year. When Nozomu walks in the door, he finds Kafuka is one of his students.

After confiding in his latest despairs to Ms. Arai, she asks Nozomu to visit one of his students who hasn't shown up to school — Kiri Komori, a hikikomori. In the end Kiri goes to school but decides to be a hikimori there. The next day, Nozomu notes that another of his students, Matoi Tsunetsuki, didn't show up that day. Ms. Arai brings Nozomu to the counseling room, where she explains Matoi's obsessive-stalker tendencies to Nozomu. That night, he attempts to dissuade her from bothering her last boyfriend; however, his strategy backfires on him. This turns him into Matoi's latest object of affection.

This episode is a pastiche of parodies about foreigners and Japanese attitudes concerning them. A foreign student named Kaere Kimura transfers into the class. Kimura is a blonde girl with multiple personality disorder stemming from cultural identity confusion. Nozumu prevents her from committing suicide but sees her underwear and is sued. While Nozomu is absent from school Chiri investigates his students and discovers that Maria is an illegal immigrant.

Chie dispatches Nozomu to investigate rumors that the invariably injured Abiru Kobushi is suffering from domestic violence. He pursues Abiru's father while he shops, causing him a great deal of inconvenience, before discovering Abiru's obsession with pulling the tails of dangerous animals. The latter half of the episode concerns Meru Otonashi, who is silent and shy in person, but remarkably abusive via text-messaging, her only means of communication.

On physical examination day, many of the girls are feeling stress about their weight, measurements and fitness. Nozumu distracts them by deciding to judge the "social worth" of students so that they will know whether they are living "above their station." Kitsu seizes on this idea, scolding everyone who possesses any luxuries, appalling Nozumu to the point where he decides to go on a hedonistic binge before killing himself. In the second half he encounters some of his students at a hot spring and is frightened to learn the spring has the power to remove their "toxicity" giving them well-adjusted personalities.

Kafuka comes down with a cold during the summer and has to go see the doctor, Mikoto Itoshiki, who happens to be Nozomu's brother. Later, Chiri and Kafuka find out from Mikoto that Nozomu has gone back to his hometown in Kuraizawa for an arranged marriage. One way or another, the girls somehow all end up arriving at Kuraizawa, where they are taken to the Itoshiki residence by Tokita. Here they find out that the Itoshiki tradition for arranged marriages simply involves both parties exchanging eye contact. The rest of the episode involves Nozomu and his attempts to avoid eye contact with the girls and various other people/objects.

Nozomu Itoshiki, a direct marketing businessman, is chased by a mysterious religious group called Hamasho. At one point, he is caught and his body is modified like a mole cricket. After his long adventure, he is discovered by Kafuka and he then becomes a high school teacher. Students in the class start calling him "Left-wing Guerrilla" (apparently in lieu of "Pink Supervisor"), making him want to die again. Right before he jumps off a cliff, Kafuka suggests he "mock marry" a girl of the Holy Nosebleed Empire. A card reveals that the entire segment is a gag based on a summary from the jacket of the manga's first volume. In the second segment, Nami Hitō, who has been missing classes, finally decides to attend her school as no one really seems to notice her absence. Unfortunately, she does not get much attention from her classmates as the high school is full of extraordinary characters. At the end of the episode, most of the major characters are introduced and Nami is labeled as the 'ordinary girl' in the school.

The first part of this episode is supposed to follow this storyline from a chapter of the Zetsubō Sensei manga. Perry has come to the school on the anniversary of the school's founding. He is an American Commodore who known for opening up Japanese ports to foreign trade (in Japanese, the phrase "opening the school" (開校?) is pronounced the same as "opening the ports" (開港?)). After he opens up various things in the school, he tries to open up Nozomu Itoshiki's mind. Suddenly, Nozomu releases a mysterious wave that reveals the dark side of the world, which is full of despair. Finally, Perry learns the lesson that he shouldn't try to open up everything in the world. However, all the characters speak unintelligible gibberish, and the subtitles suggest that Perry is Son Goku looking for the Dragon Balls and that Nozomu is an alien bent on stopping him. In the next part of the episode, Nozomu is complaining about the over-decoration of various things in Japanese society. However, Kafuka Fūra denies it, saying that it is just a trend among stylish elites. In the next part, Nozomu meets his old time friend Ikkyū-san, who likes old things. They discuss together how old things are often ignored in modern Japan. Ultimately, he wants to obtain a former-surname by marrying Nozomu's sister Rin. Rin tries to escape from Ikkyū by calling her butler, but he ends up persuading Ikkyū-san to marry her. However, Kafuka manages to find out at the end that Nozomu and Ikkyū are not old friends, but rather one-day friends during the first day of school.

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 and his students enjoy the festival of Tanabata and talk about instances where people pay more attention to the trivial details of many objects rather than the main subjects. In the middle of their conversation, which Ikkyū-san later joins, the alien race El Niño suddenly invades Japan with their mecha army. Fortunately, Chiri digs up an ancient mask and activates its hidden power to defeat the alien force. The aliens admits their mistake of paying attention to trivial aspects of Nozomu's students rather than the progress of their invasion. At the end, Nozomu and Ikkyū-san do not remember how Japan was saved from the alien invasion, as they were paying attention to trivial details of the battle scene. In the second part of the episode, Jun Kudō is reading books in the school library, while Nozumu is worried about Jun's desire to read everything in the world, which could eventually include Nozomu's own embarrassing mind. When Nozomu's other students visit the school library, Jun tells heart-warming stories that move every one of them to tears. Nozomu feels even more certain of Jun's ability to read people's minds, so he puts himself in a freezing room full of penguins to prevent Jun from reading the conclusion of the episode. The third part of the episode shows what happened between Nozomu's nephew, Majiru Itoshiki, and Kiri Komori while the alien invasion of the 'A Painter by the Roadside' episode was undergoing outside the house.

Nozomu Itoshiki and his students enjoy the festival of Tanabata and talk about instances where people pay more attention to the trivial details of many objects rather than the main subjects. In the middle of their conversation, which Ikkyū-san later joins, the alien race El Niño suddenly invades Japan with their mecha army. Fortunately, Chiri digs up an ancient mask and activates its hidden power to defeat the alien force. The aliens admits their mistake of paying attention to trivial aspects of Nozomu's students rather than the progress of their invasion. At the end, Nozomu and Ikkyū-san do not remember how Japan was saved from the alien invasion, as they were paying attention to trivial details of the battle scene. In the second part of the episode, Jun Kudō is reading books in the school library, while Nozumu is worried about Jun's desire to read everything in the world, which could eventually include Nozomu's own embarrassing mind. When Nozomu's other students visit the school library, Jun tells heart-warming stories that move every one of them to tears. Nozomu feels even more certain of Jun's ability to read people's minds, so he puts himself in a freezing room full of penguins to prevent Jun from reading the conclusion of the episode. The third part of the episode shows what happened between Nozomu's nephew, Majiru Itoshiki, and Kiri Komori while the alien invasion of the 'A Painter by the Roadside' episode was undergoing outside the house.

It's time to hand out grades, but Nozomu Itoshiki hands out completely censored report cards to his students, because he understands that majority of students do not want to be notified of their grades. He argues that people should have right to choose to be 'uninformed' of undesirable information, since they have right to be informed of desirable information. Ultimately, he tries to escape civilization to become 'free' of all the notifications in the world, but he is still in despair as nature are also trying to communicate with him. Meanwhile, Kafuka Fūra is admiring the all-knowing housewife in the neighborhood. In the second part of the episode, Nozomu Itoshiki and his nephew, Majiru, fall asleep together and have a dream where everyone's personality is reversed. The students in his dream realize that they will disappear when Nozomu wakes up, so they try to put him in an eternal sleep by murdering him in his dream. In the third part of the episode, Nozomu and his students discuss various things that are kept secret or unknown from their parents. During this section, the characters are voiced by numerous random voice actors (with most of them from the show itself), and are changed frequently.

As the school exams approach, Nozomu sniffs at the idea of good luck charms. Just then, he is arrested by mysterious people for being a potential bad luck charm for the students and locks him up in solitary, which he is quite pleased about. However, the girls break in and rescue him, and it comes to light that the students actually see Nozomu as a good luck charm. Next, everyone has different opinions of what tells them spring has come, which for some people involve strange dancing people. Later, Nami tells Nozomu she is going on a trip to find herself, whereas Nozomu says it is really a journey that exposes a person's true nature.

While watching a baseball match, Nozomu wonders about the sad fate of the multi-talented people. If a famous baseball player is as handsome as a model, is he missing a more successful career? Later on, as Kiri is taking some medicine to treat her cold, Nozomu explain to Majiru why did it took a moment for the medicine to take effect : the dreaded time lag, which can be observed in a lot of phenomenon. As the journey to find themselves continues, more of Nozomu's students embarks on the bus and procede to reveal some parts of their personality. In the end, Kafuka leads the group to expose themselves to reality and at the same time the acceptance of their true self as they are, after which she concludes by singing a heartwarming song.

As Nozomu and Kafuka attempt to find the switch to the town christmas lights, Nami finds she keep switching on other people's switches. Next, Nozomu contemplates on how people making a decision between two things subconsciously end up picking a third. He and the girls end up in a third-choice city. Whilst arguing about excessive care, Nozumu is taken by Rin to a Guardian's Club, where people take excessive care measures.

Chiri notices Nami wearing brand new trainers in the rain and gets annoyed when people don't consider TPO (a wasei-eigo term meaning Time, Place, Occassion). Nozomu laments that some people do an incorrect TPO when compensating for another TPO. When ume no hi comes, Nozomu ponders that its not a convenient holiday for prefectures of Japan that aren't next to the sea. The discussion moves onto the morals of celebrating things others can't cheer about. The gang decide to have a 'chimerical holiday', involving as little fun as possible. After escaping from the Excessive Care Guardian's Club, Nozomu finds all his leisure options restricted due to excessive care. He then notices that his body double has been benefitting everyone in his place.

Whilst complaining about how people use poetic words that make you skeptical about them, Nozomu gets thrown into a card game by Rin in which excessive writing is applied to their names. As Chiri complains about the leap seconds added at the new year, Nozomu considers there might be leap people who multiply unnoticed. Chiri is suspected of being a leap person and is enlisted into a parody of the Blue Man Group (in Japanese, blue (ブルー) and leap (うるう) have similar pronunciations). Whilst Nozomu sees Houjoue, a buddhist holiday, as a day for overlooking things, Kafka believes it should be a part of daily life, and introduces him to family that ignores life.

Since there's an outbreak of measles in town, Abiru suggests to Majiru that he should get infected right now, for it is quite worse to get them as an adult. Nozomu then proceeds to unveils many more types of "measles" you're better off to have as a kid, since their effects can be disastrous later on in your life. As Nozomu and Kafuka walks in the street, they stumble on Kanako Ōra, a laid back and careless girl from Nozomu's class, who doesn't seem to mind that a myriads of political parties uses her property's wall for their posters. As Kafuka and Nozomu continues to explore the concept of "through life", Chiri decide to label object and people so as to know who's the creator.