When it comes to Yoshiko Miyazaki（宮崎美子）, I have two images of her. One is that of her impressionable appearance on a Minolta camera commercial back in 1980. The other image that I have of her is her modest and matronly and fairly frequent stints as a current tarento on variety shows including the NHK program on Japanese names as seen below (although I know that she is also an actress).
I've noticed that her J-Wiki biography doesn't list her as a singer but she does have that experience on her resume with four singles, three albums and a BEST compilation between 1981 and 1987. Case in point, there is that debut album from December 1981, "Mellow".
To be honest, I had no idea that Miyazaki sang until I discovered some of her material on YouTube a couple of nights ago, and from "Mellow", I encountered the track "Ima wa Heiki yo" (I'm OK Now). As soon as I heard this chipper and catchy tune, I just knew that it had something to do with Yellow Magic Orchestra or one of its members. And sure enough, Ryuichi Sakamoto（坂本龍一）composed this technopop treat with Akiko Yano（矢野顕子）providing the lyrics.
Miyazaki doesn't have the most expressive vocals but I think that rather suits her within a technopop tune since I think at the time with such acts in Japan and other nations, the vocals have often played second fiddle to all of the fascinating bleeps and bloops of the synthesizers (Yano and Taeko Ohnuki excluded). Still, I think that Miyazaki has a pleasant high and breathy quality to her voice, and I believe that is Yano helping out on background chorus.
As for "Mellow", looking at the "Music Avenue" blog, it looks like Miyazaki was surrounded by a lot of big-time songwriters. In addition to Yano and Sakamoto, Yuming（ユーミン）, Yoshitaka Minami（南佳孝）, Junko Yagami（八神純子）and Takuro Yoshida（吉田拓郎） were also contributing their time and energies to the tracks.