Seiso Academy is a prestigious high school that sorts students into two majors: General Studies, characterized by distinct grey uniforms, and Music Studies, characterized by pristine white uniforms. While rushing to class one morning, General Studies student Kahoko Hino has a chance encounter with Lili, a small fairy searching for someone with the ability to see her. Lili flies away, and Kahoko, puzzled by their meeting, continues on her way.

Later that day, the participants of a school-wide music competition are announced, and all of them are, unsurprisingly, Music Studies students—at least until Kahoko's name is read out. Immediately tracking down Lili, the small fairy gifts Kahoko a magical violin and convinces her to participate in the competition.

Kiniro no Corda: Primo Passo follows Kahoko's endeavors alongside Lili, as the young student must now face the challenges of competition and go head-to-head against her competitors while navigating a new world of classical music.

[Written by MAL Rewrite]

Years ago, the opening of an interdimensional portal released two beasts into the skies over the Sea of Japan, visible to all the countries along the coast. After destroying the naval patrol sent to investigate the disturbance, the two beasts then turned against each other. Witnessing the fight from Japan, scientists Joe and Marie Hayakawa were sucked into the rift. Upon returning to Earth, they compiled and published the academic findings from their voyage in a legendary book titled ''Day of Succession''. Attempting a second expedition to that other dimension twelve years later, the couple have not returned. Twins Ai and Yu Hayakawa decide to set forth in search of their parents and the mysterious Wonderland they studied. In the ruins of an abandoned subway station, the two wait for a train to take them to the world beyond. On board they meet Lisa Pacifist, who quickly decides to aid the two in the search for their missing family. Can the three of them manage to find Joe and Marie?

Miyagawa Atsushi is an 11-year-old boy who is 180 centimeters tall. Since he has a grown-up looking build but acts his age, he has always been running into troubles. On the other hand, his 17-year-old elder sister Atsumi is only 137 centimeters tall. Even though she has a childish looking build, Atsumi takes good care of Atsushi.

The cast is back and ready to quip! In this companion film that follows season 2 of the zany, irreverent Seitokai Yakuindomo anime series, the student council must again grapple with a mix of double-entendres and doubly potent teen hormones.