Sono Koe de, Sono Uta wo.

Hoshika Tsukimino is a high school girl who admires Sakuya Ookuchi, the vocalist of the world-famous band Lucifer. She gathers members to audition for a band produced by Sakuya, but their vocalist quits at the last minute. In the process of searching for a new vocalist, Hoshika learns of new voice actor Maon Mizuki, a classmate who always wears a face-mask.