Yamasa Soy Sauce Factory — 400 Years of Fermentation

Yamasa Corporation, founded in 1645, is one of Japan's oldest soy sauce breweries and the largest in Choshi — a city that produces 20% of Japan's soy sauce due to abundant quality water and proximity to soybean shipping routes. The Yamasa factory compound covers 12 hectares and includes Edo-period fermentation warehouses built from cedar and clay, now designated cultural properties.

The factory offers free guided tours (Japanese only, but English pamphlets provided) through the brewing process: soybeans are steamed, mixed with roasted wheat and koji mold, then fermented in massive cedar barrels for 6-8 months. The scent inside the fermentation warehouse — deep, salty, slightly sweet — is overwhelming and unforgettable. The tour ends with tastings of multiple soy sauce grades, from light usukuchi to rich tamari.