Humanity Has Declined

In a world where mankind is nearing extinction, the main character, a girl who acts as a mediator with fairies, is sent to turn butcher chickens, but the chickens escape. After some strange FairyCo products show up in the village, including a tonic that restores her hair, the heroine, her grandfather, and her assistant go to a fairy factory where mass-produced fairy products are made.

The heroine and her assistant become lost after being separated from her grandfather and the receptionist. She soon gets separated from her assistant and comes across the factory's manager, who directs her to an off-limits area so she can try and find the upper management. She soon discovers the factory is run by a group of intelligent plucked chickens who plan to take over the world. They are soon stopped by the arrival of the assistant and his camcorder, which drives them to commit suicide. After freeing all the trapped fairies, the heroine finds that her hair has been brought to life due to the tonic.

A woman named Y who supposedly works in researching the Human Monument manages to find a disc full of data inside an old mansion, which turns out to be a volume of a yaoi manga. She soon gets into the habit of publishing yaoi manga which she distributes across the country. When the fairies catch wind of the trend and start publishing their own yaoi manga, Y begins to work harder to compete, bringing about a manga renaissance. However, her manga becomes too heavy that the couriers do not want to deliver the boxes themselves, leading her to create a dōjin fair. Some time later, the heroine discovers a mysterious dōjin which traps her and Y inside a blank panel.

Exploring the strange world they wound up in, the heroine and Y encounter her assistant, who had also gotten himself stuck. They deduce that in order to proceed through the panels, they must do something dramatic enough to make a printed sound effect materialize. They also realize they can draw things into existence, as well as understand that if their manga becomes too boring, they will descend into cancellation. As such, the trio start going through various genres to make it through the manga world. After encountering some fairies, they realize that in order to escape, they need to reach the ending, though a desire for ratings soon leads the stories into a complicated mess. The manga soon becomes unpopular and ends up getting cancelled, but thankfully they manage to end up back in the real world.

As the village prepares an electric-powered festival for the Human Monument Project, the heroine hears from the fairies that they are leaving to avoid the electromagnetic waves from the festival that are deadly to them. They leave behind a good luck charm and a curious manual explaining the dangers that come if no fairies are met during the day. During the festival, the heroine meets a curious girl named Pion, who is searching for her companion. The next day, the heroine and her assistant are sent to explore an underground structure, where they get trapped. As they search for the exit, the charm the heroine received turns into a fairy who tries to lead them towards water but instead comes across a group of acidic slimes. As they face more dangers upon reaching a computer room, they are rescued by Pion.

As Pion, revealed to be a robot who the heroine now calls P-ko, joins the party, they encounter her companion Oyage, a similar robot who calls himself O-taro, who wants to abandon his mission and live in the strange city. As he sends a killer digger truck after them, they all fall down a hole, winding up at an underground castle. The heroine and assistant are confronted by O-taro, who combines with the slimes to become a "Killer Death Cat", though the fairies step in to help them. With help from the fairies, P-ko manages to defeat O-taro using a super-powered microwave, which in turn restores their memories. After the gang manages to escape the city, it is revealed P-ko and O-taro, whose real names are Pioneer and Voyager, were deep space probes that gained humanoid form. O-taro makes P-ko realize that deep inside, like himself, she does not want to leave the warmth of the solar system. Hearing these thoughts, the heroine sabotages the electric generator, stopping P-ko and O-taro from being able to leave before reworking them to become wind-up powered.

As the heroine is sent by her grandfather to look for his assistant, she encounters someone who looks exactly like her. Things only get stranger as she has déjà vu after déjà vu, encounters various versions of herself, and finds her memory less and less clear. She soon learns it to be the work of the fairies, who are manipulating time in order to get several copies of the heroine to make sweets for them. After several loops resulting in hundreds of clones making sweets, the heroine soon encounters a village full of dogs where the assistant lies.

As the heroine reflects on her multiple timeloops, she focuses on the details about the assistant given to her by her grandfather and the doctor looking after him. During a certain timeloop between the fourth and fifth times, the fairies make a bug which takes the heroine "far away", where she encounters a boy whom she thinks is the assistant, and finds him to be an excitable and lecherous young boy who calls himself the Ringo Kid. It turns out that Ringo Kid was the younger version of the heroine's grandfather from the distant past. After hearing more about him from her doubles during the fifth time, the heroine meets the assistant on the sixth. She finds him to have a more gentle and plain personality, and believes he had finally found his true personality using doubles to gather opinions from others about how he should be.

After an increase in fairy population leads to bullying, the heroine is sent to accompany asylum seeking fairies to find a new home for them. Through various circumstances, the heroine ends up stranded on an island in the middle of the ocean, along with a group of pessimistic fairies who declare her the queen of their new nation. The fairies' motivation to work on building their new nation soon increases their population. The nation evolves into a bustling civilization dedicated to serving its queen, who begins living in luxury. Upon cultivating a plant that can produce candy, the fairies' research and development soon turn the nation into a literal candy island. However, after a lapse in judgement causes everyone to build monuments everywhere, the island is soon ruined and made devoid of food and water, sending them into poverty. The heroine feels she and the asylum seeking fairies should leave the island, but they remain trapped by a rainstorm caused by the collective depression of the fairies. After the island ends up collapsing on itself, the heroine returns to dry land and her daily life.

The heroine begins her job as a mediator and finds it not to be what she expected. Whilst observing an abandoned site, she encounters a group of fairies and brings some of them home with her. After getting over their initial worries, the heroine finds the fairies to be quite talkative and curious. She gives them some names, only to be tasked with naming all the other fairies as well. Finding the abandoned site turned into a metropolis overnight, she gives the fairy population a naming dictionary so they can decide on their own names. The next day, the heroine finds herself hailed as a god and ends up causing chaos when she tries to pass the responsibility onto someone else, leading to the city's destruction.

The heroine thinks back to when she was ten and began attending school, having to start at the lowest grade... As she decides to remain inconspicuous and focus on skipping through the grades, she finds herself the target of bullying from some of the other students, including a young Y. Believing her to be the mastermind, she finds herself alienated from a girl called "Curly" who was trying to become her friend. One day, the heroine rescues a fairy from a group of bullies and has it tag along with her. As the stress of her school life leads the heroine to admit to herself that she feels lonely, the fairy does something before disappearing. The heroine finds Curly has joined her in skipping grades, also facing some bullying from jealous peers. As the heroine decides to repay some of her kindness, she finds Curly to be disturbingly affectionate with her. Curly then moves into the heroine's dorm and invites her to join a secret organization called the Wildrose Society.

Whilst spending time having tea parties with the Wildrose Society, the heroine learns that Y was once part of the society. A year later, the heroine moves up to year 4 and becomes Y's classmate. She soon learns Y had been stealing books to build her own yaoi library. In exchange for not revealing her secret, Y sneaks the heroine into the rooms of the other Wildrose members, revealing their hidden agendas, including how mentally unstable Curly is. After learning all of this, the heroine joins Y in searching for a true fairy tea party, and over the years they rekindle their relationships with the Wildrose Society members. As the heroine, Y and Curly discover a room full of robots, the heroine remembers about the fairy she met years ago. After everyone graduates and the school is torn down, the heroine is visited by Y, who brings her the robot from the school dorms, which is soon revealed to contain the fairy she had met at school.