Chiba has two soy sauce towns, Noda and Choshi, and both of them sit on water. Noda is caught between the Tone and the Edo. Choshi stands at the mouth of the Tone, where the river meets the Pacific and the wind comes straight off it.

Why there, and not somewhere else? Three things happen to coincide. The soybeans and wheat could be had from Hitachi, just to the north. The climate suited the work: off Choshi the Kuroshio and the Oyashio currents meet, which keeps the gap between summer and winter narrow and gives koji mould and yeast an easier time of it. And the finished barrels could go down to Edo by boat, which in the seventeenth century was the only sensible way to move anything that heavy that far.

Ingredients, weather, and a road made of water, all arriving in the same place at the same time. The breweries lined up accordingly, and stayed lined up for three centuries. The switch from barley to wheat in the mash is what made the dark koikuchi style possible in quantity.

The larger works still run tours, and you can watch the mash going in and the pressing coming out. A certain amount of what soy sauce tastes like was decided by the shape of a river.