Eir Aoi previously performed the second opening theme song to the first Sword Art Online TV anime, the opening theme for the Sword Art Online EXTRA EDITION special, as well as the first opening theme to Sword Art Online II.
Japanese record label SACRA MUSIC alongside Aniplex revealed tonight that Japanese singer Eir Aoi will be returning to the Sword Art Online franchise, performing the new theme song for the upcoming anime film Sword Art Online -Progressive- Scherzo of Deep Night, the sequel film 2021’s Aria of a Starless Night.
She continued with the franchise for the 2015 video game Sword Art Online: Lost Song, of which her song “Cynthia no Hikari” was used as the theme.