Just like any other high school student, first-year Uta Komaki wants to make the most of her youth. With her namesake talent in singing, she attempts to join her school's light music club but repeatedly fails due to her extreme shyness and lack of confidence. Intimidated by the dazzling presence of the club's members, Uta fears to even submit her application.

One day, Uta receives an invitation from Airi Kojou, president of the a cappella club, to check out their club instead. Unlike the light music club, this group performs purely without instruments. Uta soon finds herself amazed by the way the members' voices resonate with one another—delicate yet cohesive, resembling a mille-feuille dessert's thousand layers. Moved, Uta takes a quiet step forward into creating a harmony where everyone shines together.