Sake, its history in Japan, the unique brewing process, and microbes concerned with the characteristics of flavor are described. The main flavor components derived mainly from the fermentation process are higher alcohols, isoamyl acetate, ethyl caproate, and phenethyl acetate. These are the compounds which give an accent to the flavor of sake. The esters are formed mainly by yeast during mash fermentation. Isoamyl acetate is produced by the reaction of acetyl CoA with isoamyl alcohol catalyzed by alcohol acetyl transferase. The enzyme, bound to the yeast cell membrane, is unstable to heat and unsaturated fatty acids. The ester formation is regulated by the amount of isoamyl alcohol produced. Acyl CoA alcohol acyl transferease catalyzes the formation of ethyl caproate from caproyl CoA and ethanol. In this reaction, the amount of caproyl CoA supplied is important. The mechanism of higher alcohol formation, including the biosynthetic pathway of amino acids and its feedback regulation, is discussed. Finally, breeding and the practical use of sake yeast with high productivity of higher concentrations of higher alcohols and esters are described.