The story- Master Jianzhen spreading soy sauce to the East

Although originated from China, Japan is the one that took soy sauce to the next level. Soy sauce nowadays has become a part of Japanese diet, representing their food culture. There are many versions as for when the soy sauce was introduced, most people place the time at Tang Dynasty, while others, Song Dynasty.
The Tang Dynasty, the most powerful in Chinese history, is regarded as a high point in Chinese civilization. Japan dispatched many scholars and monks to China during this period of time to study Buddhism and their culture. When these people set sail back home, they brought along with them some recipes, which included the methods of sauce production. The Japanese dubbed the sauce from China the “Tang sauce”, to mark the difference between the “Korean sauce” from Korean Peninsula. The “Tang sauce”, nonetheless, is not soy sauce, as where “Korean sauce” is actually miso, whose pronunciation was from Korean, meaning “sauce”.
It is said that Master Jianzhen was the one who introduced soy sauce to Japan during Tang Dynasty. When the master and his disciples came to Japan to help further the diffusion of Buddhism, Chinese medicine, pastry, soybean, black bean, and the methods to produce sugar, tofu, and soy sauce (some said miso) were introduced to the locals around the 8th century. 

Another story- Introduced by Zen Master Jiau Shin

Zen Master Jiau Shin came from Japan to China during the 13th century (Song Dynasty) to study Buddhism. He stayed at the Jing Shan temple to further his practice, during which he learned how to produce miso. Returning home, the Zen Master lived in a temple at Yuasa Kishu (located in Wakayama Prefecture), and started to teach the villagers how to make the Jing Shan temple miso. Later, he found that the residue in miso buckets could be used as a seasoning. He then heated up the miso, stopped the fermentation, and added more water. Another type of liquid condiment came into being—miso-tamari—which is the ancestor of Japanese soy sauce, signaling the beginning of Japanese soy sauce. Yuasa is now recognized as the birthplace of Japanese soy sauce. Through online search, we discovered the soy sauce museum at Yuasa, where a series of events have been held. Please check out the websites below.

Website of Yuasa soy sauce event	Video about Yuasa soy sauce

The widespread of soy sauce

Japanese soy sauce is originated from Kinkichihou, but as the population increased in Kanto (because Tokugawa Ieyasu established the Edo period in Kanto), the soy sauce industry relocated. The Koikuchi developed in the Kantō region has been considered as the typical Japanese soy sauce. In the wake of the Meiji Restoration, soy sauce production has become mechanized. Scientific approaches were adopted, such as fast fermentation method, the use of defatted soybeans as raw material, increasing production, shortening production hours, and developing various flavor or products with local characteristics.

In recent years, soy sauce has become a commodity in the United States, with Kikkoman Soy Sauce being the most popular brand. Kikkoman Corporation has entered the US market well before its popularity among westerners. The company has first seized the opportunity, changing the formula of the product so as to cater to the Americans and the taste buds of those meat lovers. This approach has made soy sauce a part of US food culture. Furthermore, as eastern cuisine spreads to the west, the westerners have welcomed the indispensible soy sauce with open arms. The soy sauce consumption in US alone, has reached over 100 million liters, and is on a yearly increase.