Rieko Sakamoto joins a Kiba district elementary school as music teacher in 1956 Tokyo. Fueled by her desire to honor her older brother Masaki Sakamoto – her moral mentor who vanished as a kamikaze pilot in World War II – she dedicates herself to preserving traditional Japanese children's songs as vital cultural identity. She focuses this commitment on preparing the school choir for a regional competition, aiming to foster community pride and unity amid Japan's difficult post-war reconstruction.

She quickly recognizes Shizu Miyanaga's vocal talent and integrates it into the choir. When student misconduct involving Akira Yanagisawa and Gonji Abe threatens participation, Rieko faces profound professional disappointment. Shizu Miyanaga's subsequent death in a marine accident delivers another deep personal and professional blow.

Following these setbacks, Rieko supports the students' campaign to reinstate the choir's competition entry. She channels the collective grief over Shizu's death and adapts to Gonji Abe's abrupt transfer into renewed determination for the choir's success. Her approach consistently embodies perseverance, cultural continuity, and quiet resilience, progressing from personal loss toward finding purpose in guiding the next generation through tradition amidst societal change.