Si ha notizia di salse fermentate a base di soia in Cina da circa 1.000 anni, ma la salsa di soia come la conosciamo oggi nacque in Giappone nel XIII secolo per merito di un monaco buddista che si stabilì nella cittadina di Yuasa. Oltre sette secoli dopo il processo di lavorazione della salsa di soia si svolge immutato.
Yuasa, a small coastal town in Wakayama Prefecture, Japan, is a fishing port and the producer of one of Japan's most well known mandarin oranges, the Arida mikan. But a stroll through the traditional streets, including the only stretch of the famous Kumano Kodo pilgrim route that runs through the center of a town, takes you back to an age before westernization, when Yuasa was a vibrant hub of gastronomy in Japan. For it was here, in the 13th century, that soy sauce as we know it was first established and produced, and even now the streets are rich with the smells of fermenting soy sauce, still produced exactly the same way it was more than 750 years ago.