In the classic tradition, a true demi glace is a mixture of equal parts sauce espagnole and veal, beef, brown or chicken stock, which is then reduced by 1/2.
There are a very few "legitimate" variations. Some cooks call a glace of appropriate concistency, but made without an espagnole a demi, but it's really a kind of glace de viande.
Now that we've got the French out of the way, let's start on the Japanese.
Hime, you're looking for a particlular Japanese demi-glace flavor profile. Whether or not that's the same thing as the westerm demi-glaces with which I'm familiar, is anyone's guess.
I'm pretty sure I've posted a recipe for sauce espagnole a couple of years ago. If not, and you want one, I'll be happy to oblige although it may be a few days before I get to it. Also, there's nothing special about my recipe, with the possible exception of my usual exhaustive description of technique. Otherwise, it's very traditional and straight ahead.
Anyway, the whole espagnole and demi-glace things start with copious quantities of good stock. If you don't make your own stock, you may want to rethink the whole project.
PS. Hime, since writing this I found the "running recipe" I'd already posted on CT; knocked it up into standard recipe format; and posted it in the "Recipes" thread. Enjoy.