It took me the purchase of "Japanese City Pop" to find out that R&B singer Hitomi "Penny" Tohyama（当山ひとみ）even existed, and just out of pure luck, browsing through YouTube unearthed her older sister, Keiko "Myrah" Tohyama（当山恵子）. There was some more digging for me to find out that Myrah was indeed Penny's older sister.
The anthropological dig continued as I gradually found out that perhaps the elder Tohyama released one single and one album...at least. The one single apparently was released in 1984 and was titled "My Guy ~ Cafe Sign", a mellow ballad with a hint of Motown in its music and lyrics by Yoshihiro Yonekura（米倉良弘）, the same fellow who came up with "Sexy Robot", Penny's song that I wrote about last night.There was one other person involved in the lyrics but unfortunately I couldn't read his kanji due to the size of the photo of the liner.
Myrah has a slightly higher voice than Penny, and she definitely has got that feeling of some of that 70s soul. "My Guy" is also a track on that first (and perhaps sole) album "What Can I Do?". From what I've read, both the single and album are the rarest of the rare.