Mayumi Itsuwa 五轮真弓

She's very popular in the 1980s but is unheard of now, her music
being drowned by the new-waved jpop and kpop.
This is from wiki:
Mayumi Itsuwa (五輪
真弓, Itsuwa
Mayumi?) (born January 24, 1951)
is a Japanese vocalist, composer, lyricist, and keyboardist who made her debut
in 1972.
Her first studio album entitled Shoujo was recorded in
Los Angeles, produced by GRAMMY Award winner John Fischbach, with
distinguished musicians such as David Campbell, Carole
King and Charles Larkey who was King's husband at
that time. Owing to her introspective compositions, Itsuwa was
often nicknamed "Japanese Carole King", along with other Japanese
singer-songwriters like Yumi
Matsutoya (who had worked under her birth name "Yumi Arai" during
the mid 1970s) and Minako
Yoshida.
Itsuwa has gained moderate success on the Japanese albums chart
in her early career, and received massive popularity and acclaim
through a single "Koibito yo" released in 1980. A song topped the
Japan's Oricon chart for three consecutive weeks, and won the 22nd
Japan Record Award for "Gold
Prize" in a same year.[1][2]
It was covered by the country's legendary singers including
Hibari Misora and Noriko Awaya in later years,
and became a signature song for Itsuwa.
After "Koibito yo" became a hit, Itsuwa gained popularity also
in non-Japanese Asian countries during the 1980s.
In Indonesia,"Kokoro No Tomo" and "Amayadori" become the most
popular songs ever released by her. In 2006, Mayumi Itsuwa and
Delon Thamrin recorded an
Indonesian and Japanese version of the song. This was later
included on the 2006 compilation album "Duet Love Songs".
Her songs:-
恋人よ
(yoibito yo)
潮騷 (shiyo sai)
雨の中の二人 (ame no naka no futari)
Dakishimete (hold me
tight)