As someone involved in the adoption process in Japan you are very incorrect--
there is adoption in Japan, it is just very difficult to do.
There are Japanese as well as foreign children available for adoption in Japan. Adoption in Japan is a difficult process (especially if you are not Japanese) but it can still be done.
The heart breaking thing is that children must be adopted by the time that they are six years of age (or 8 if they have started the adoption process before they were six), if they are not adopted they end up in the "system" and spend their lives in an institution with little hope for their future.
You can read more by visiting the US Departmen of State's web site on adoption in Japan at:
Intercountry Adoption Japan
Or you can do a search on "Adopting in Japan" on Google to find many other sites giving the same information.
I wish I could find the site again, but there are also a few women (married to Japanese men) who adopted Japanese children who were not related to either the husband or the wife.