mentions the popularity of small mini velo bicycles in Japan. These are small wheeled bicycles that may or may not be folders. They include some of the folding bicycles we're familiar with in the U.S. and Europe, but there are many bicycles such as the Bianchi Novita shown here that are made exlusively for the Japanese market. You can see the whole catalog of mini velo Bianchi bicycles at Bianchi's Japan distributor.
Gios also has a mini velo collection in their Japanese lineup. Check out the Louis Garneau branded mini velo bicycles. There are also Renault Cycles Citadin 16 and Citadin 18 lines.
There are probably hundreds more models of Nihon-no mini velo jitensha bicycles like these. I've seen a few of these bikes make it here to the United States, where I see them occasionally on Caltrain during my commute in the San Francisco Bay Area.