Kou Yaginuma's initial inspiration for the story came from a statement he once read describing the Hohner Little Lady harmonica as one of the first musical instruments taken into space. However, as an aspiring manga artist, Yaginuma had neither resources to conduct research on nor knowledge pertaining to spaceflight. He also hesitated to write the series because his own life experiences did not reflect the dreams of his characters. Despite these challenges, Yaginuma found comfort in the determination of his characters, especially that of Asumi Kamogawa.