Th is chapter explores the reason why songs sung by voice actors/actresses, which are oft en called “animation songs” and abbreviated as “ ani-son ,” have gained popularity in Japan, by examining historical changes in both the music industry and the animation industry. Voice actors/actresses are those who play voice roles of characters in animation works. Much discussed these days are voice actors/actresses who are engaged not only in voice acting, but also in singing. Such actors/ actresses are referred to, here in this chapter, as singing voice actors/actresses. Today, many voice actors/actresses are engaged in singing as part of their professional career with their songs almost always ranking high in music charts in Japan.