Sake ingredients

Question

Sake or Japanese rice wine, is made of three key ingredients: water, rice and Koji. Sake consists of 80% pure water. Koji is steamed rice inoculated with the powerful Aspergillus oryzae mold. When combined with rice, it breaks up the long chain of starch molecules, which ordinarily yeast alone can not. The question is less about kashrus ingredients but the status of this beverage as Yayin.