EW. This stuff is GROSS. Fermented soy beans? Basically, rotting beans... Ugh. How can anyone eat this? I think I would vomit if I tried. Has anyone had this?
From Wikipedia:
The first thing noticed by the uninitiated after opening a pack of nattō is the very strong ammoniacal smell, akin to strong cheese. Stirring the nattō produces lots of spiderweb-like strings. The nattō itself has a nutty, savory, somewhat salty flavor that belies its odor.
Nattō is most commonly eaten at breakfast to accompany rice, possibly with some other ingredients, for example soy sauce, tsuyu broth, mustard, scallions, grated daikon, okra, or a raw quail egg. In Hokkaidō and northern Tohoku region, some people dust nattō with sugar. Nattō is also commonly used in other foods, such as nattō sushi, nattō toast, in miso soup, salad, as an ingredient in okonomiyaki, or even with spaghetti or as fried nattō. A dried form of nattō, having little odor or sliminess, can be eaten as a nutritious snack. There is even nattō ice cream.
Nattō is often considered an acquired taste and the perceived flavor of nattō can differ greatly between people; some find it tastes very strong and cheesy and may use it in small amounts to flavor rice or noodles, while others find it tastes "bland and unremarkable", requiring the addition of flavoring condiments such as mustard and soy sauce. Many non-Japanese find the taste very unpleasant, while others relish it as a delicacy. Some manufacturers produce an odorless or low-odor nattō. The split opinion about its appearance and taste might be compared to Vegemite in Australia and New Zealand, blue cheese in France, lutefisk in Norway and Sweden, Mämmi in Finland and Marmite in the UK. Even in Japan, nattō is more popular in some areas than in others. Nattō is known to be popular in the eastern Kantō region (Tokyo), but less popular in Kansai (Osaka, Kobe). About 236,000 tons of nattō are consumed in Japan each year.
