Jun is a very intelligent little girl who spends her time arranging all kinds of inventions. It goes until creating two small robots, Kichinosuke and Yukinojo, who become her best friends. Because of her intelligence, Jun gets into college at a young age and she meets and falls in love with a boy from her class who's called Zero. Zero is interested in motorbikes and not in school and is accustomed to not attending the courses. He got delayed in his schooling and thus is found much older than the other students and is there for humiliated for it. On the other hand Jun is way too young and little to be in college and is made fun of. Thanks to their common passion for mechanics, Zero will sympathize with Jun and will agree to dine with her in Harbor, the restaurant where Jun's parents live. This is long series of fun adventures and arguments that little Jun will make to allure her charming prince, who's twice older than her.

The protagonist of the story, Konoha Inoue, is a seemingly normal senior high 2nd year student. His high school life, other than a hinted incident 2 years ago, can be summed up as normal- if one can dismiss the secret fact that he used to be a female bestselling romance author. Due to that incident, however, he has now vowed never to write again. This continued on until he was forced to join the literary club by the literary club president, the 3rd year female student Amano Tooko, a beautiful girl who has a taste for eating literary works. Now he has been tasked with writing her snack every day after school.

The rare and inexplicable Puberty Syndrome is thought of as a myth. It is a rare disease which only affects teenagers, and its symptoms are so supernatural that hardly anyone recognizes it as a legitimate occurrence. However, high school student Sakuta Azusagawa knows from personal experience that it is very much real, and happens to be quite prevalent in his school. Mai Sakurajima is a third-year high school student who gained fame in her youth as a child actress, but recently halted her promising career for reasons unknown to the public. With an air of unapproachability, she is well known throughout the school, but none dare interact with her—that is until Sakuta sees her wandering the library in a bunny girl costume. Despite the getup, no one seems to notice her, and after confronting her, he realizes that she is another victim of Puberty Syndrome. As Sakuta tries to help Mai through her predicament, his actions bring him into contact with more girls afflicted with the elusive disease. [Written by MAL Rewrite]

New Beastars sequel.