I'd like to add a more specific question:
Does anyone know whether the nattou sold in the aforementioned stores is fresh or not?
By "fresh" I mean made locally, or made in Japan but not frozen on its way here.
(AFAIK, nattou is akin to yoghurt and yakult in that it contains live bacteria which are extremely beneficial to our organism Hence I don't think it is wise to eat deep-frozen nattou as the bacteria would all have perished, wouldn't they? )