Natto is clearly one of the traditional Japanese foods that is a mainstay of Japan's culinary culture.
However, it cannot be called something that is unique to Japan.
Foods that are similar to natto are found in other parts of East Asia, as well as in Southeast Asia, the Himalayas and so on. These foods have been prepared in the traditional manner and eaten in these areas as well, not only in Japan.
In addition to Japan, Natto culture is firmly established in countries such as Thailand, Nepal, Vietnam, Myanmar, Bhutan, South Korea and China. Natto culture has been passed down primarily in the mountainous regions and basins in the interior of these countries.
Even within the same country, however, most of the people living in coastal regions where there is abundant seafood do not make or eat natto, and they may have never even seen it. The people in these regions have no lack of excellent umami seasonings such as fish sauce. (As has been noted in the section on natto culture, natto is considered to be an umami seasoning.)
Moreover, it is difficult to identify the regions where natto culture has been passed down by drawing lines on a map.
This is because the Himalayas and other mountainous regions are home to many ethnic minorities that extend across national borders, each with its own customs and culinary culture. In the case of natto as well, these cultures differ in terms of whether or not they make or eat natto and, if they do make natto, what plant they get the natto bacillus from and so on. Even the names they use to refer to natto are different: each ethnic group or region uses a different one of the more than 25 names for natto.
The only thing that is common to all of varieties of natto in Asia is that it is made from soybeans.
The Island Nation of Japan
Since natto exists throughout Asia, can we assume that it spread to the island nation of Japan from somewhere in Asia? Or did natto travel to Asia from Japan?
Again, this question cannot be answered, since the origin of natto is unclear.
However, researchers who have conducted fieldwork in Asia on the origins of natto in each region have discovered that there were three distinct mechanisms at work. In some cases, natto spread to that location from other areas. In others, natto was spread from enclave to enclave by the migration of peoples. In still other cases, natto appears to have developed independently by the people in that region. ("The Origins of Nattto" NHK Publishing, Inc.)
There are many examples of Japanese traditional foods that originally came to Japan from China and were modified in unique ways. Natto may be an example of this phenomenon. Or it may have been "discovered" by accident one day in Japan.
Natto Along Japan's Lengthy North-South Axis
If asked "where is the birthplace of natto in Japan," most Japanese people would reply "Mito." Mito, a city in Ibaraki Prefecture, was one of the first places to feature the small-bean natto that is now the dominant variety of natto, and it was instrumental in the spread of natto nationwide in the modern era. However, it cannot be said definitively that Mito is the actual birthplace of natto.
The Japanese archipelago stretches for a considerable distance north to south. Along this axis there are many differences in culinary culture and many variations in preferred flavors, so different ways of eating natto developed in each region. There are also areas in which there was no culture of eating natto. In coastal regions and other areas with abundant sources of protein and dashi (soup stock) with umami flavor, there was no reason for natto to become established.
Now, of course, natto is appreciated throughout the country, both in the north and in the south.
