The most popular song by Yumi Matsutoya & Masumi Okada's is 恋人と来ないで (Don’t Come With Your New Girlfriend / Koibito to Konaide)
Yumi Matsutoya & Masumi Okada's first song 恋人と来ないで (Don’t Come With Your New Girlfriend / Koibito to Konaide) released on Mon Dec 01 1980.