Thanks to local bike store Citizen Chain and the bike coalition's winterfest, I've now got a "new" bike! I just took it for a ride to Golden Gate Park, and wearing my green jacket, I looked just like Christmas. It's a mint-condition, vintage 1979 Japanese bicycle. From what I can tell, "Mikado" was a minor bike line, and the Mikado Bicycle Division was a small part of Toyoda America, Inc. (an importer of Japanese manufactured goods, which must have translated the bike's Owner's Manual). Toyoda America, Inc. is still around, only now it's called Toyota Tsusho America, Inc. and it's owned by Toyota. So I guess my new bike is a Toyota.
A Massachusetts cyclist named Sheldon Brown - who, sadly, died in 2008 - has interesting background on Japanese bicycles at his website.
The bike comes with a cartridge-type Shimano three-speed hub. I got the paperwork on that, too, and it's copyright Dec. 1978.