“Niji no Oto” is the sixth single released by Aoi Eir and 8th digital single. It was released in a Limited Edition <Anime Edition> (CD+DVD) only. The title track was used as theme song for the anime special Sword Art Online Extra Edition. The b-side, “Yume Sekai”, is a cover of the the song of same tittle by Tomatsu Haruka, which was originally used as first ending theme for the anime Sword Art Online.
Catalogue No. SECL-1446～7
Release Date: 1st January, 2014