And here I thought that the only singer by the name of Kosaka I knew was Akiko. Well, I've now got a second Kosaka...Kyoko Kosaka（小坂恭子）, to be exact. A couple of years after Akiko Kosaka（小坂明子）wowed the masses with the evergreen ballad "Anata"（あなた）as her debut, her unrelated namesake, Kyoko Kosaka from Miyazaki Prefecture released a successful ballad of her own as her 3rd single from May 1975.
Titled "Omoide Makura" (Pillow of Memories), I actually heard the song a few times over the decades but neither knew the title nor the singer. Singer-songwriter Kosaka has been described on J-Wiki as a folk and New Music singer, but I think with this song, she's probably more in the former category and I'd say that it also enters the genre of Mood Kayo. Kosaka's lyrics have the heroine reminiscing about some pillow talk memories with a past lover...probably not a song for daytime karaoke, not because it's particularly racy but the mood suits a nighttime session with a tumbler of the good stuff.
I don't know how far "Omoide Makura" got on the Oricon weeklies although it ended up as the 3rd-ranked song for 1975 so I'm fairly sure it reached the top spot. It sold 850,000 copies according to the same company although other data has said that it actually went over a million. The song also got onto Kosaka's 2nd album, "Kyoko" which came out in October 1975.
And it seems like a lot of other singers have done their own karaoke session on a grander scale. Here is Masako Mori （森昌子）.