Tomoko Suzuki, Juri Ueno, and a class of schoolgirls drift through a languid summer makeup class, their attention pulled in by curiosity and mischief rather than by lesson plans. When the school brass band heads off to perform at a baseball game and leaves behind their bento lunches, the group seizes the chance to pitch in. They persuade their math teacher, Tadahiko Ozawa, Naoto Takenaka, to let them deliver the meals, hoping for a small, silly diversion in an otherwise uneventful day.
On the train, they sample the lunches and gradually fall asleep, only to wake with a shock: they’ve missed their stop. They trudge back to the band’s destination, lugging empty stomachs and heat-streaked hopes, only to find the meals wasted by the tropical summer. The meal mishap makes most of the group sick, with one notable exception: their cymbal player, Nakamura, Takuo Nakamura, Yuta Hiraoka, who somehow escaped the feast’s aftereffects.
Takuo then organizes an audition for replacements to play at the upcoming baseball game. Only three girls show up: two former punk-band members and the shy Kaori Sekiguchi, Yuika Motokariya. The others are dragged into the process by pressure and fear of punishment for the food-poisoning incident, and the ensemble initially lacks musical focus, joking around with their instruments while Kaori stands out with a quiet, serious talent. Faced with a shortage of players, Takuo decides to transform the group into a big-band outfit and pivot toward swing jazz, hoping that a bold shift might salvage the opportunity.
The girls throw themselves into practice, and Kaori’s budding talent begins to lift everyone’s spirits. They discover the joy of playing together, and a sense of camaraderie starts to knit the group into Swing Girls. But the day before the big game arrives a cruel setback: the original brass band members recover, and the newly formed swing trio—plus their few remaining players—are left decimated and uncertain about their chances.
A new school year rolls in, and Tomoko makes a drastic personal move to fund their dream. She sells her family's PlayStation 2 along with her computer setup and buys a used tenor saxophone, only to discover that the instrument’s low B-flat pad is already failing. While she practices, she spots Takuo at his keyboard, and the two share a brief, intimate duet of Take the "A" Train, a moment that marks a turning point in their musical journey. The Swing Girls begin the process of purchasing their own instruments, pooling money through supermarket jobs and other odd tasks.
Missteps continue to surface as they work toward stability. A cooking demonstration at the store spirals out of control, triggering the sprinkler system and wiping out several of their wages. Undaunted, they spend a day mushroom-picking for matsutake and even fend off a boar that threatens their crops. One girl’s quick thinking leads to a reward, and the prize money funds a batch of cheap, worn instruments that the two rockers manage to repair with the help of their ex-boyfriends, who operate a wrecking yard. The group is finding its voice, and their music begins to take shape in small, imperfect steps that feel like real progress.
The club, now officially dubbed Swing Girls, makes its first public appearance. The performance is imperfect, but Kaori receives encouragement from an anonymous jazz fan. When the group tracks down the admirer, they discover he’s not a distant critic but Mr. Ozawa himself, a man with a vast collection of jazz records and the belief that he can guide them to something authentic. He agrees to lead the band, injecting his passion into their rehearsals and helping them refine their sound.
As the band’s skill grows, they decide to submit an audition tape for a music festival. Tomoko is left in charge of the submission, but she accidentally sends the tape too late, and the group faces rejection. Nakamura, in a quiet moment, confesses that Mr. Ozawa is not a professional saxophonist but an enthusiastic amateur, and the revelation nearly derails the team. Embarrassed, Ozawa asks Nakamura to keep the truth quiet as he steps back from the festival.
On the way to the festival, Tomoko admits that the Swing Girls may not have a formal place there. Snow interrupts the trip, halting their plans, and their spirits dip. Yet Ms. Itami, Miho Shiraishi, arrives on a bus with news: another band canceled because of the weather. She rushes to ferry the Swing Girls to the competition, and they scramble onto the stage just in time. The performance that follows wows the audience—classmates, Ms. Itami, and even Mr. Ozawa—proving that their raw, unpolished passion can carry them to a bright, hopeful future.
What began as a chance to chase a simple errand becomes a journey of friendship, persistence, and a stubborn insistence on finding one’s own voice. The group’s missteps are many, but their willingness to improvise, to rally around a shared dream, and to grow together turns a summer misadventure into a genuine and lasting musical awakening.
