As I've mentioned before regarding Momoe Yamaguchi's（山口百恵）career, there was the first half in the early 70s which was characterized by the young high schooler singing in that higher tone, sometimes with some rather suggestive lyrics while the second half had her transform into a far more jaded, seen-it-all figure with a bit more gravel in her vocals.
"Arigato, Anata" (Thank You, Darling), the B-side of her 10th single from September 1975, "Sasayaka na Yokubo"（ささやかな欲望...A Humble Desire）, is from the earlier part of her career, and I first heard it on a highlight episode of "Sounds of Japan" involving the singer. It's instantly recognizable from that emotional trumpet which launches things as Momoe wishes a departed love well with his future. The ballad just wears its heart right on its sleeve with the horn section and the shimmery strings which really play up the bittersweet lyrics. It was the last collaboration between composer Shunichi Tokura（都倉俊一）and lyricist Kazuya Senke（千家和也）for her; the two had worked together on nine of Momoe-chan's first 10 singles.
Yamaguchi had also been carving out a prolific career as an actress on TV and in movies, and one of her major projects involved something called the "Akai Series"（赤いシリーズ...The Red Series）. Spanning from 1974 to 1980, this was a series of 10 half-year dramas for which the singer ended up appearing or starring in a little over half the programs. "Arigato, Anata" happened to be the theme song for the second in the series, "Akai Giwaku"（赤い疑惑...Red Suspicion）which also starred her future husband, Tomokazu Miura（三浦友和）as a medical student. This particular drama was probably one of the more bittersweet episodes in the series as Miura and Yamaguchi fall in love only to have a case of Cobalt 60 throw a spanner deep into the works.
Keep the tissue ready here. The theme song was quite apt for "Akai Giwaku", and the whole single did well on the charts, hitting No. 5 at its peak and becoming the 59th-ranked single for 1975. Both A and B sides also made it onto Yamaguchi's 7th album from December of that year, "Sasayaka na Yokubo" which managed to get as high as No. 15. I've yet to hear that A-side incidentally which I'll have to do, but "Arigato, Anata" is another wonderfully sepia-toned 70s song for me.
I also featured a Momoe song which was also a theme song for the third entry in the "Akai Series". You can have a look at it right here.