Production begins with the intricate preparation and then fermentation of the ‘black koji rice’. The rice is polished, steamed and coated with a microbe called black koji, which imparts unique flavors, distinctive aromas, and helps to break down starches into sugars. The black koji is given time to propagate over the steamed rice, and must be closely tended to by the ‘koji master’. After two days, it is ready to be mixed with soft spring water from nearby Black Hair Mountain, along with a touch of yeast, which helps to convert the sugars into alcohol. This initial fermenting mash of ingredients is known as the ‘first moromi’.

Koji is an essential ingredient in the production of shochu and helps to distinguish it from all other spirits. Black koji in particular - and in contrast to the more commonplace ‘white koji’ - creates the distinction of a deeper, more complex, craft shochu.