While preparing for a class play, centaur Himeno Kimihara, who is playing the princess, ends up kissing her demon friend Nozomi Gokuraku after a male classmate who had originally hoped to play the prince role modified her script. During the play, a set of steps collapses beneath Himeno and Nozomi, forcing Himeno to make a daring rescue to save Nozomi. Later, during marathon practise, Nozomi and their half-Satyr friend Kyouko Naraku test how fast Himeno can run, which almost results in an accident.

After finding Himeno modelling in a fashion magazine, Nozomi is roped into trying out some different fashions by Mitsuyo Akechi and her girlfriend Inukai after they hint Himeno might get expelled for having a part-time job. She later learns, however, that Himeno's modelling work was simply an unpaid favor for her mother's friend, while Mitsuyo was secretly working at a part-time job the whole time. On a cold day, Himeno and friends try to warm themselves up by thinking back to when their class went to a school for merfolk to attend their classes.

Himeno goes out with her cousin Shino and comes across student council president Manami Mitama and her three triplet sisters, Chiho, Chinami, and Chigusa. Shino gets defensive about how the triplets go about kissing others, which isn't helped when Mitsuyo and Inukai provide their own input on the matter. Later, the triplets are tasked with looking after their youngest sister Sue while Manami is out doing student council work. Sue becomes too weak to play outdoor games with the triplets' friends, but she manages to play house with someone, which they later discover might have been a zashiki-warashi.

After being approached by a boy with a love letter, Himeno is reluctant to accept it because she is worried about how her horse half would look naked. Hearing about her complex, Nozomi and Kyouko propose that they look at each others private parts to put Himeno at ease. After being assured that she is perfectly normal, Himeno accepts the love letter only to find the boy was only interested in her for her breasts. Later, Himeno and Kyouko try to help Nozomi study for her make-up exams, during which Nozomi believes she sees a UFO. The next day, Himeno's class receives a new transfer student; an Antartican snake girl named Quetzalcoatl Sassassul.

Himeno feels intimidated by Quatzalcoatl because of a scary B-movie she saw about snake people as a child. After hearing about this, Quetzalcoatl requests to watch the movie in question with Himeno, assuring her that her species is nothing like the monster featured in the movie and managing to become friends with everyone. Later, Quetzalcoatl clears up the misunderstandings and rumors surrounding Antarcticans with her classmates. Afterwards, Quetzalcoatl, feeling unnerved following a news report of an alleged Antarctican UFO attack, joins Himeno and the others as they go clothes shopping.

As the girls discuss what kind of hairstyle would suit Himeno, she explains how her ancestry led her to have red hair. Meanwhile, Kyouko acts as a secretary for her mangaka father while Manami is sent to deal with an allegedly cursed box before criticising her father for being stuck between being a good father and being a painter.

The girls all go to the pool, where Sassassul overcomes her fear of water and understands more about Manami's sisters. Later, the girls help the Occult Club hold a night of telling scary stories to help the president, Towako, get along better with everyone, though the subject quickly switches to science.

Himeno goes to an archery meet with her underclassman, Ayaka Wakamaki, who acts strict towards her. Following some advice on her friends, Himeno helps Ayaka to loosen up by offering to go on a date with her. Later, the mermaid school holds a festival in which one of the mermaids has to perform a song to appease the god Tagon. The festival is interrupted, however, when a large fish monster posing as Tagon appears.

Himeno and the others are chosen as a prepatory committee for Jean Rousseau, a French-raised amphibian politician who is scheduled to give a speech at their school. While visiting his homeland prior to his speech, Jean is concerned by his people's willingness to rage war against mammal-based lifeforms. Many years ago, a young angel boy is captured and forced to work in an internment camp. As the boy becomes weaker and filled with despair, he is given food by a centaur who is regarded as a traitor among his fellow prisoners, convinced that those with good hearts need to survive. Just as the federation army raids the camp to rescue the prisoner, the boy finds the centaur hung by the other prisoners, who attempt to kill him as well before he is rescued by a kind soldier. This allowed him to grow up into a kind-hearted politician who is accepting of all races.

Hime, Nozomi, and Kyouko decide to tail after Sassassul as she goes on a supposed date with a boy to a contemporary art museum, unaware that various organisations are keeping an eye on her too. At the same time, Manami goes on a date to the same museum with her boyish classmate Makoto Omaki, getting into a conversation about her father's art career.

After learning about different types of grass and flower from Himeno, Shino attempts to explain the concept to her classmates at kindergarten.

The girls participate in an RPG fantasy setting, fighting against monsters in a dungeon labyrinth, which turns out to be a story written by Mitsuyo.