Another accidental find from YouTube, it had been a long time since I put up anything by vocal group Hi-Fi Set（ハイ・ファイ・セット）. This is "Moeru Aki" (Glowing Autumn), which was a B-side of their 13th single from November 1978, "Nettaiya"（熱帯夜...Tropical Night）and was also the theme song for the movie of the same name. I tried to look up information about that movie but the J-Wiki article just seemed to go into the making of the movie itself rather than what the story is about.
My impression from the title and the melody by Toru Takemitsu（武満徹）, though, is that the movie was another one of those bittersweet romances with plenty of ennui. The ballad certainly has that European flavour with hints of Henry Mancini jazz and soaring orchestra, and the vocals by Hi-Fi Set are wonderful as usual with lyrics by Hiroyuki Itsuki（五木寛之）.
The music that starts off each verse though reminded me of the intro for Teresa Teng's（テレサ・テン）classic "Tsugunai"（つぐない）which was released some years later.