Somebody hand me a mic...
As you may already know, if you follow anime, "J-pop" music, or Japanese entertainment generally, female singing duos are very much a part of the scene [as are "idol singers" in groups of anywhere from one (solos) to five]. Nemoto Mitsuyo and Masudo Keiko were friends from their high school days and decided in 1976 to take part in an "audition program" called Sutaa Tanjou <Star Birth, or, if you like, A Star is Born>. Apparently, they were a success, as they debuted later that year as Pink Lady; they went on to record many albums and became one of the most famous duos of the '70s. (They were so popular that an anime series about them, Pinku Redi no monogatari: Eikou no Tenshitachi <The Pink Lady Story: Angels of Glory>, ran on Japanese TV from October 1978 to June 1979.)
Even after they retired as a pair in 1981, they each went on to perform as singers and/or film actresses. They even staged a successful comeback in 1996 to serve as a guide and inspiration to the current generation of idol singers.
You can see much more about Pink Lady at Jeffrey Branch's site, Pink Lady: The Web Site (from whence these photos came)
You may also wish to visit Pink Lady's international fan site
Some of the information for this page came from the Famous Japanese site