For sake, "Yellow Koji mold" is usually used.
But this sake also uses another type of Koji called "White Koji mold."
These two have different characters, and they are mixed with good balance.
Yellow Koji mold: Normally used for sake. It gives mellow taste and sweet aroma like chestnuts. White Koji mold: Mainly used for Shochu. It gives rich and dry taste with citric acid.