The process involves blending moisture into the tea leaves. The mixture is then hit with highly heated steam and sterilized. After that, Kuro-koji bacteria is evenly added to inoculate the mixture. A machine then monitors the heat of the pile during fermentation and automatically mixes it if its temperature exceeds a certain point. Once fermentation is complete, the process is ended by being again sterilized with highly heated steam. The leaves are then roasted to complement the aromatics brought out in the koji fermentation.