Gukganjang

Soup soy sauce or "guk-ganjang" is a type of Korean soy sauce (ganjang) made entirely of fermented soybeans (meju) and brine. It is also a byproduct of doenjang production. Both lighter in colour and saltier than other Korean ganjang varieties, soup soy sauce is used mainly in guk (soup) and namul (a seasoned vegetable dish) in modern Korean cuisine. Soup soy sauce is referred to by many different names. In the English-speaking world, it is most commonly known as "soup soy sauce", which is a direct translation of guk-ganjang (국간장). The name "soup soy sauce" is used because it is used mainly for soup in modern Korean cuisine. Also, it is the name used by many popular soy sauce brands such as Sempio, Daesang's Chung Jung One, and CJ Cheil Jedang's Beksul. Other names for the sauce include: The earliest soy sauce brewing in Korea seems to have begun prior to the era of the Three Kingdoms. The Records of the Three Kingdoms, a Chinese historical text written and published in the 3rd century, mentions that "Goguryeo people are good at brewing fermented soy beans", in the section called Dongyi (Eastern foreigners), in the Book of Wei. Jangdoks used for soy sauce brewing are found in the mural paintings of Anak Tomb No. 3 from 4th century Goguryeo.

Source: Wikipedia