Akira Yanagisawa is the class deputy at an elementary school in Tokyo's Kiba neighborhood during 1956, a time as Japan emerges from post-World War II poverty. A bright student showing leadership potential, he often hesitates to challenge group consensus, mirroring the era's social dynamics. His working-class family includes his carpenter father, Genji Yanagisawa, mother Fukuko, older sister Kazuko, and younger sister Reiko; they live in a community where household telephones are rare luxuries.

His story unfolds around the school choir competition led by teacher Ms. Sakamoto. Akira connects with Shizu Miyanaga, a new transfer student from Kobe, through shared musical interests. After an incident involving Akira and his friend Gonji "Gon" Abe, leader of a local children's group, the school faces disqualification from the regional chorus tournament. This coincides with Shizu's sudden death in a marine accident, deeply affecting Akira. Moving past his initial shock, he advocates for the choir's reinstatement, persuading school authorities. This action marks his growth in confronting challenges and honoring Shizu.

The choir's renewed participation becomes a collective effort to process grief and affirm cultural continuity. Akira collaborates with classmates and Ms. Sakamoto, reflecting themes of communal resilience in post-war Japan through preserving "Doyo" (Japanese traditional children's songs) as cultural identity.