The main ingredient in a traditional Japanese miso soup is miso paste, which is a fermented soybean product. Miso paste is made from soybeans, salt, and a fermentation starter called koji, which contains mold. The fermentation process gives miso its unique umami flavor, which is essential to the soup. Miso soup typically also contains dashi, a broth made from kombu (sea kelp) and bonito flakes, along with other ingredients like tofu, seaweed, and scallions. This soup is a staple in Japanese cuisine, consumed daily by many, and is notable for its health benefits, including probiotic properties.