The Japanese fermented soybean dish known for its strong smell is natto.
Natto is made by fermenting whole soybeans with Bacillus subtilis var. natto. The process gives the beans a powerful aroma, a distinctive flavor, and a sticky, string-forming texture. It is commonly eaten for breakfast, especially with rice, and may be seasoned with soy-based sauce, karashi mustard, or chopped Japanese bunching onion.
Natto is particularly associated with eastern Japan, including the Kantō and Tōhoku regions and Hokkaido. Its smell and texture make it an acquired taste, although many people enjoy it as a regular part of their diet. Stirring the beans produces the characteristic strands that distinguish natto from other fermented soybean foods.
Miso is also fermented from soybeans, but it is a paste made with salt and kōji, usually used as a seasoning. Tempeh is a compact fermented soybean cake associated with Indonesia, while kimchi is a Korean fermented vegetable dish. Natto is therefore the only option that matches both the soybean fermentation and strong-smell clues.