Shimoneta: A Boring World Where the Concept of Dirty Jokes Doesn't Exist

Tanikuchi Okuma enrols in the country's leading elite public morals school from a much lower-ranked one, out of admiration for the student council president Anna Nishikinomiya. It is the morning of the first day of school, and on the train there, he notices a male student looking at him intently, who is later accused by a woman of molesting her. He knows that this isn't true (the woman is just trying to extort the guy) so he makes a distraction, making people think that he was the molester. As he tries to get away he is surrounded by security, but the notorious terrorist Blue Tundra suddenly appears and makes an even bigger distraction that allows him to escape. When Okuma arrives in school it is obvious that there are many students who are badly repressed, such as Fuwa Hyouka, who is obsessed about how babies are really made. He is summoned to the student council and called upon to help assist investigation of the incidents of terrorist indecency that have been occurring lately. Anna directs another member of the student council, Kajou Ayame, to show him the ropes. It turns out that Ayame is none other than Blue Tundra, and she blackmails Okuma into assisting with her terrorist plots. Blue Tundra's next operation occurs during a student assembly, where she drops sexy pictures and shows a film of copulating flies to her making lewd noises, which has a terrible effect on the badly repressed students.

Ayame once again gets Tanikuchi to assist her in her terrorist plots, first finding a cache of pornographic magazines, surreptitiously duplicating them and hiding them in various places around the school for students to find. The student council secretary Gouriki distrusts him (despite being the one he saved from accusations of molestation at the train), and he tells them that his father was, like Ayame's, an activist against the new laws that created the censorship state, and was arrested and imprisoned as a result. He was ostracised for much of his childhood and only Anna, whom he met in kindergarten, showed him any kindness, so ever since he distanced himself from his father's ideology. This convinces the council of his sincerity. There is an upcoming health examination at the school, and Anna's mother has a new bill in the wings that will tighten social control still more. Ayame performs another terrorist plot that involves conducting an "eye exam" that will make the students read individual letters and explain the actual process of making babies using what is considered obscene language, without tripping off their collars. He is chased by Anna and Gouriki and very narrowly escapes capture, but from a distance a student sees him remove his disguise.

Anna has been receiving letters from a stalker, but she keeps this secret from the rest of the council, although everyone can tell that she is troubled by something. Saotome, the much-admired artist of the school, tears up an award she has been given. She blackmails Tanikuchi into cooperating with her plans to get closer to someone she loves, as she saw him remove his disguise after the last terrorist incident. She confesses that she loves Anna as well, forcing Tanikuchi to tell her that he loves Ayame instead. Ayame comes up with a plan to catch Anna's stalker, by posing as her boyfriend and provoking the stalker into revealing himself, with Gouriki watching ready to apprehend the stalkers should they arrive. Both Tanikuchi and Saotome are also watching on the sidelines. The plan works, and the stalker reveals himself, and Ayame manages to subdue him, but there are two more stalkers present. Tanikuchi manages to subdue one them but is struck in the process, and as he falls he lands on top of Anna and winds up kissing her. He is badly injured, but Anna is deeply affected by the kiss.

Tanikuchi is in the hospital after being injured by the stalkers, and is concerned that Anna has never visited him even once since the incident. After his release, he learns that Anna has made the school crackdowns on indecency even more severe, and that he appears to have suddenly become the target of another stalker himself. Ayame continues her terrorist plots and learns of a stash of true hardcore pornography that somehow escaped the purges, and she plots to have the students discover it but Sophia Nishikinomiya has arranged an event promulgating even harsher measures on the same day. Ayame has also convinced Otome to join their cause as an erotic artist, but she has an artistic block and needs to see such indecency live in order to draw it. To get the latter to happen she has Tanikuchi invite his stalker in while Otome watches in an adjoining room. The stalker turns out to be none other than Anna, who, being excessively repressed and ignorant of the nature of her sexual urges strips naked and tears off his clothes, and very nearly has intercourse with him right there and then, but Ayame suddenly arrives and she runs off.

Tanukuchi is jarred by Anna's behaviour, and cannot accept that the pure, sweet girl he admired has an irrational, perverted side. She constantly stalks him, preventing him from distributing the pamphlets with Otome's indecent drawings and the instructions on where to find the stash of pornography, and even threatens Ayame with scissors as it seems she is too close to him. He drops the batch of pamphlets in Hyouka's lab after Anna confronts him one more time. Thus thwarted, Ayame and Tanukuchi try to recover the porn themselves, although this is clearly impossible for them to do alone, as there are many guards at the grove where it is hidden. However, Hyouka distributed the pamphlets herself and arrives with a large number of students, who serve to distract the guards as Ayame and Tanukuchi enter and don their SOX disguises. Anna is there however, and she fights Ayame, while Tanukuchi recovers some of the pornography and a BDSM costume that he incorporates into his SOX disguise. Though he is conflicted, he helps Ayame fight Anna, who falls down a hill into the grove. The students who participated are arrested and forced to sign their support for the more repressive law Sophia is sponsoring. SOX however, managed to steal the students' signatures and replaced them with dirty pictures, so Sophia finds herself in trouble for public display of indecency and her efforts at passing the law are thwarted for the time being.

SOX is scheming to rebuild various types of sex toys that have long been banned, based on descriptions in the stash of pornography they recovered, as well as others from oral tradition. They have Hyouka make a few remote control vibrators, and as Tanukuchi is getting ready to take them, Anna barges in, so he has to make excuses to her for why he is meeting with Hyouka. He says he was asking advice for a gift he was planning to give Anna, which she takes to be the vibrator, and he makes her think is a sort of a charm stone. She is happy to take it and later turns it into a pendant. The next day, Anna calls them to the student council for a meeting, when the pendant/vibrator turns on unexpectedly. This drives her into a frenzy, and the remote control doesn't seem to work, so he tries to escape and ask Hyouka to help fix it, which she cannot without the actual unit. Anna catches up to him, and he is driven into a corner and she embraces his lower half, the vibrator stimulating him nearly to the point of climax, but it breaks down just in the nick of time.

There has been a recent rash of underwear theft incidents in the school and Anna has ordered an investigation. These incidents are being blamed on SOX causing the group's reputation to fall among the students, so Tanukichi and Ayame investigate the matter seriously. They stake out the girls' changing rooms in an attempt to catch the thief, and when Ayame comes closer to investigate, Anna molests Tanukichi again until Gouriki comes by. After recovering Tanukichi comes to check on Ayame and finds she is confronting Hyouka, who is hiding a yaoi manga by Otome starring characters clearly based on himself and Gouriki, which he confiscates and destroys. Meanwhile, Anna and Gouriki have managed to capture a large group of the underwear thieves, who are identified by a projection of their leader as members of a group called Moist Throng, saying that they are inspired by SOX. Ayame is incensed as this Moist Throng seems to have a far more radical agenda than SOX, and the reputation of their group is suffering by association, so they resolve to stop them somehow. After the meeting Tanukichi runs into a young girl named Onigashira Kosuri who is on the run from the moral police, and he helps her escape, and tells him that she is the daughter of Onigashira Keisuke, the secret financial backer of many naughty terror groups, and that she is trying to join SOX. Ayame, though sceptical and suspicious of her reluctantly allows her to join the group.

Kosuri is staying in Tanukichi's apartment for the time being, and Anna, unstable as always, breaks in and finds them sleeping together. He introduces Kosuri as his little sister, which mollifies Anna somewhat but she still stabs the floor around Kosuri, making her fall into unit below. The Public Morals Committee has also assigned a trained disciplinary officer to the school named Tsukimigusa Oboro, who sees indecency everywhere, but actually proves remarkably easy to manipulate. Later, SOX has a meeting, and Ayame explains that their next mission is to infiltrate the nearby Zoushigaoka Academy and try to at least get some of their dirty pictures in. Kosuri says she will take care of it and three days later she has outdone herself, having produced accurate information on the school that will allow them to distribute their pornographic pamphlets without detection. Kosuri begins to boss it over on Tanukichi, and she explains how she managed to infiltrate the school by deviously manipulating the student council members' feelings, and he objects, saying that Ayame would never approve of such methods that involved hurting people. She says that he would not expose her actions to the woman he loves, as it was evident to her that he is in love with Ayame.

Ayame hatches a plan to disassociate Moist Throng and SOX. Reasoning that they seek out the underwear they steal by smell, they use Tanukichi's underwear as bait. Ayame goes out as Blue Tundra to distract the PMC and the Student Council, while Tanukichi sets the trap, while Kosuri and Otome secretly go around hiding more dirty pictures around campus. The plan does not quite work when Anna is drawn by the scent of Tanukichi's underwear instead, believing it to be her reward, and is crestfallen when he tells her that it was a trap for Moist Throng. Actual members of Moist Throng steal the underwear from Anna, who chases after them. Although the plan did not quite work, Ayame says that a lot of good came out of it: it showed that they can use Tanukichi's underwear to distract Anna and get the student council off their tails. They repeat the plan the next day with this in mind, using Otome's underwear as the real bait for Moist Throng instead. The plan goes remarkably well, as Tanukichi manages to subdue many Moist Throng members, until at the girls' changing room while tying up one of them, the power is cut as the fire alarm sounds. He encounters Oboro, and exposes him as a man. Anna comes in soon after to change her clothes made wet by the sprinklers, and Tanukichi makes his escape by tossing her his underwear. It turns out that Kosuri had spoken to Fuwa and asked her to bring the Moist Throng students to the changing rooms where Tanukichi had been waiting, and she had also activated the fire alarm as a distraction. This concerns Ayame because it complicated the plan, establishing a link between SOX and the regular student body through Fuwa, and the fire alarm caused the incident with Oboro and Anna. Later, they receive a note from the leader of Moist Throng and have a confrontation with him at the park.

The meeting between SOX and Moist Throng's leader goes badly as the two groups are unable to settle their differences, and the leader leaves, hinting that they are planning something big. The next day, the monorail system has broken down and Tanukichi has to rush to get to the bus. Gouriki is on the same bus and he tells him that power to the monorail was sabotaged. Ayame calls him, warning him that he must not use the buses, but one of the Moist Throng terrorists has revealed himself, hijacking the bus and threatening all the passengers with a gun. 42 such buses were hijacked. Hyouka realises that the terrorist on her bus has a fake gun, and that permits the other passengers to subdue the terrorist. Anna goes berserk and beats up the terrorist on her bus. The terrorist on the bus with Gouriki and Tanukichi is disgusted on seeing Gouriki wearing only his underwear that he is likewise subdued. Told that there is actually one gun among the 39 remaining buses that is real, the authorities are forced to tread carefully. Tanukichi meets up with Ayame and they come up with a plan to apprehend Moist Throng and its leader White Peak themselves, thereby dissociating them from SOX. They use Kosuri's panties as bait to lure the bus with White Peak away, and moving quickly, Tanukichi boards the bus and fights White Peak but winds up getting beaten up. Ayame arrives in her Blue Tundra disguise and the two of them manage to subdue White Peak, but Kosuri betrays them and knocks Ayame out of the bus, while the PMC chases her away. Kosuri declares herself for Moist Throng.

Kosuri also gets Tanukichi to leave the bus, and she and White Peak bring their bus to Zoshigaoka Academy, where White Peak, in his guise as the student Ichinose Takuma, studies. Moist Throng has taken about 500 hostages and the PMC has besieged the campus. They have demanded food and drink for the hostages as well as a mass of new panties, threatening to publish compromising pictures of the hostages otherwise. Kosuri soon realises that she made a mistake betraying SOX for them, as she learns that Takuma and Moist Throng are not the revolutionaries looking to change the country she thought them to be, but just common perverts out to sate their lusts until the PMC decides to break through. She is bound and gagged as a hostage after she unsuccessfully attacks him. Meanwhile Tanukichi and Ayame get in contact with each other and formulate a new plan. They receive a call from Saotome who is among the hostages, and she provides intelligence on the conditions inside the school. Although Tanukichi has his reservations about this plan which goes against his ethics, he disguises his scent by constantly washing himself and goes to Anna, convincing her to temporarily ally with SOX to defeat Moist Throng and retrieve his underwear which they have stolen. Anna, Gouriki, and Oboro join Ayame and Tanukichi and together they manage to defeat Moist Throng.

The members of SOX receive an invitation to the Nukumi Resort allegedly from Sophia Nishikinomiya. Tanukichi remembers how his father had given him a valve handle for use if he should ever go to Nukumi. This makes them decide to go there despite their misgivings. At the resort they see Gouriki and Anna, who have received similar invitations. They go to the baths, where Anna has entered the men's side in an attempt to seduce Tanukichi, but as she does this, they hear Sophia just outside being attacked by someone. They see her at the entrance to the baths, unconscious, and dressed in black underwear. She too received an invitation to go to Nikumi, allegedly from Anna, which she claims she never sent. They meet the one who sent the invitations, a man covered in black panties. He has taken all of their clothes and left them black underwear to wear instead. The man in black explains how the valve handle Tanukichi has is the key to a great treasure, They manage to escape, recovering the valve handle, and explore the ruined buildings to find a place where it will fit. They find a valve stem that fits it exactly, and turning it, they find a treasure trove of erotic art that had been hidden from the censorship state. They seal it back up again, hoping that it can be opened in the future when the country is ready for it.