You should be aware that Japanese Economics isn't the same as Economics. I remember going to a Japanese job fair in Boston back around '98, the Nihon Keizai Shinbun had a sign up (in kanji only, of course) offering interviews only to native Japanese PhD economics graduates of Harvard. Well jeez, why didn't they just call Harvard and directly contact the 1 or 2 people who qualified?
If I were in your position, I would probably start by looking into Japanese universities with prominent Econ departments (i.e. Todai), search their websites, maybe try to develop a contact there who can offer guidance. Or maybe the Ministry of Finance would be a good place to look around. You really need to develop contacts to get a "madoguchi" into a serious organization, like your friend did.