Plot
A class of schoolgirls are bored during their summer make up class. When the school brass band leaves to perform at a baseball game without their bento lunches, Tomoko and the other girls persuade their math teacher, Mr. Ozawa, to let them deliver the lunches. On the train, the girls fall asleep after eating one of the lunches and miss their stop. They walk back to deliver the bentos to the band, but they have spoiled in the summer heat, and all but their cymbal player, Takuo Nakamura, who missed out on his meal, fell ill.
Takuo holds an audition for band replacements to play at an upcoming baseball game. Only three girls audition: two former members of a punk band, and the shy Kaori Sekiguchi. Takuo confronts the other girls, threatening to turn them in for the food poisoning in if they do not join. The girls have no musical experience and clown around with their instruments, except for Kaori. As they are several members short of a brass band, Takuo decides to turn the group into a big band and perform swing jazz.
The girls train hard for the performance. Kaori's talent inspires the others, and they come to enjoy playing. However, on the day before the game, just as the girls have become confident, the brass band members recover and the girls are devastated.
As the second school semester begins, Tomoko sells her family's PlayStation 2 along with her computer and its peripherals, and buys a used tenor saxophone, which she soon damages, breaking the low B-flat pad. While practicing, she discovers Takuo playing his keyboard and they share a short duet of Take the "A" Train. The members of the swing band gather at school and decide to buy their own instruments. The girls get supermarket jobs to earn money, but Tomoko and several others lose their wages when a cooking demonstration gets out of hand, triggering the store's fire sprinkler system. The remaining girls spend a day picking matsutake mushrooms, but are attacked by a boar; one of the girls accidentally stomps and crushes its skull. However, they claim reward money, as it had been destroying crops. With the money, the girls buy cheap, but damaged, instruments, and the two rockers convince their overly affectionate ex-boyfriends, who operate a wrecking yard, to repair them.
The group, now dubbed Swing Girls, play their first public show; the performance goes badly, but Kaori is given advice by an anonymous jazz fan. When the group approach him, he runs away. They chase him to his home and discover that he is Ozawa, who possesses an extensive collection of jazz records. Assuming he is an expert saxophonist, they convince him to lead the band.
The band's skills improve and they record an audition tape for a music festival. They leave Tomoko in charge of the tape, but she sends it too late and the band is rejected. Tomoko is too embarrassed to tell the others. Nakamura discovers that Ozawa is not really a professional saxophonist and is in fact an amateur student himself. Embarrassed, Ozawa pleads with Nakamura to keep it a secret before quitting the festival performance to the girls' shame.
On the train to the music festival, Tomoko confesses that the band have no place at the festival, and the train is halted by snow due to debris on the tracks. Initially disappointed by the news, the band decides to play in the train anyway. At that moment, their teacher Itami arrives in a bus and informs them that another band has cancelled due to the snow and rushes them to the festival. The Swing Girls rush onstage just in time and perform their set, impressing the audience including their classmates, Itami, and Ozawa.
