Tenshi, Ei-chan, and Shiratori all attend Kawagoe Academy. One day, they get pulled into the orbit of former conductor Haruo. He drags them into his newly founded boys choir where they suddenly find themselves performing a song in front of an audience!

Are you Cardbocchi-kun's friends?
أأنتما صديقا صندوتشي-كن؟
Sind das deine Freunde? Ihr solltet
auch an meinen Übungen teilnehmen.
¿Son amigos de Cartoncito?
¿Sois amigos de Cartoncito?
Vous êtes ses amis ?
Venez en cours, vous aussi.
Siete amici di Danbocchi?
São amigos do Papelão?
Вы друзья Коробочки?