"Japayuki" is the Tagalog slang word for Filipinos who are working, or who have worked in Japan. Specifically, this refers to Filipinas who have worked as "cultural dancers" or other similarly financially rewarding jobs in the offshore entertainment industry. The moniker usually sticks with the person for the rest of his/her life (as snickering neighbors say "japayuki kasi" when someone wonders where they got enough money to buy a new house/car/whatever).
GABRIELA, a women's-rights organization, estimates over half a million overseas contract workers leave the country each year; a good number of them end up in Japan, to work the bars. See gn0sis' writeup under "the lucrative way to visit Japan" for additional information.
A lot of them fall prey to con artists and illegal recruiters - most pay around PhP5,000-15,000 (about US$100-300, about an entire month's salary for a schoolteacher) for the papers (passport, visa, health checks, etc) and sometimes, dance lessons. If they're lucky, they end up with an honest agency that doesn't dump 'em at Narita without a job, money, or anybody to call. If they're even luckier, they don't end up at a Yakuza-owned establishment, to be sold into white slavery.
Although most of the women (and the few (5%) men) who sign up to become japayukis are well aware of these risks, they still keep coming. A bar worker can make around US$2,500 or so a month - nearly PhP125,000 at current (2001) exchange rates, and far more than what stockbrokers or middle management would make in Manila. Most of those who end up with good jobs stick around for a year or two to build up their nest egg, then invest in small businesses or real estate back home.
A friend of mine who spent a year in Tokyo as an exchange student told me that once people found out she was a Filipina, they immediately assumed she was a "hospitality girl". This opinion was immediately reversed when they found out she was going to college on a full scholarship - apparently, college grads aren't as plentiful in Japan as they are here.
Also see "Brunei baby" as a similar, though less-used term.
Figures copped from a GABRIELA pamphlet, the rest from friends and relatives.