I'm at risk of sounding like a know-it-all here, but I just can't let you guys stay all mixed up like this without trying to correct it.
Koreans don't use KOJI.
So don't even go there. Some store might have NOO ROOk.
That's what they use to make rice wine.
I've tried 2 Japanese stores today to fine KOJI.... No luck yet.
[SOAPBOX]
Koreans
do use
koji when they're making sak, and some pretty darn respectable sak is indeed made in that country. To further clarify on the subject of that moldy rice:
if you are not using koji, you are not making nihonshu (sak).
To be sure, there are other styles of
jiu that don't use
koji. The Korean homebrew
makgeolli (or
makkoli, depending on who you talk to) uses
nuruk and usually baker's yeast.
Nuruk is a kind of diastatic granola made from wheat and barley malts, and it's none too sanitary when you consider you're using it entirely on the cold side of brewing this style of
jiu. The resulting room-temperature fermented beverage is so sour that it's almost always sweetened with sugar before being consumed, and a significant portion of it ends up being distilled into
soju - the Korean analog of Japanese
shochu.
Those yeast balls mentioned in the last few posts of this thread are
jiu-men, that might help you guys who are looking for them. They contain yeast, flour, and a laundry list of microorganisms that can saccharify rice starches (
koji is not necessarily one of those critters), though usually only amylose.
Jiu-men is used to make Chinese style
jiu:
huangjiu,
nuer'hong, and
huadiao jiu. Because the the rice of choice for these products is the amylopectin-packed "glutinous rice" (more properly called "waxy rice"), the resulting
jiu is usually very sweet.
[/SOAPBOX]
Cultural differences between Anchorage, Alaska and Sydney, Australia aside, every time I've asked for
koji in an Asian market I've been met with blank stares. In my experience, the employees of those shops are about as familiar with that product as anyone else. You can try showing them a picture, or you can just check the refrigerator case next to the
miso.
Koji is used to make
miso, so it's usually kept near those products since it also requires refrigeration.