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.
Itsuwa gained moderate success on the Japanese albums chart in her early career, and received massive popularity and acclaim through the single "Koibito yo" released in 1980.
[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 2006, Mayumi Itsuwa and Delon Thamrin recorded an Indonesian and Japanese version of the song.