Founded in 1827, Matsuai makes this extraordinary shoyu by cold-fermenting its flagship Marudaizu Koikuchi Shoyu for ten years or more. The long maturation makes the shoyu thicker while producing incredible umami and deep, layered flavors and aromas. It is a dark style shoyu, or “koikuchi.” 

The soybeans and wheat are grown by contract farmers in Kumamoto who do not use any pesticides or chemical fertilizers, which is Matsuai's policy.