Sake is alcohol obtained by the function of yeast, one of microorganisms, which decomposes the sugar into alcohol and carbonated gas (carbon dioxide). Generally, carbon dioxide, the byproduct, is released during the stages of pasteurization and filtering. However, in recent years, sake containing carbonated gas has gained popularity year after year. There are various types of sparkling sake, ranging from a soft mouth-feel and slightly effervescent type, which is often available at the beginning of the new sake season, up to kassei nigori (cloudy sake) close to unfiltered sake called doburoku. It is brewed in several methods: bottled while yeast is alive in order to leave bubbles, or filled with carbonated gas to control the bubbles, or added with a little bit of yeast and sugar when bottled, just like champagne, to undergo secondary fermentation in the bottle. In each method, there are two types, the one removing sediments called ori, and the other without removing ori. An increasing number of sake breweries started to produce sparkling sake, and in 2016, those focusing on sparkling sake established the Japan Awasake Association for the purpose of improving the quality and promoting dissemination. It has attracted attention in Japan and abroad as sake which sparkles to enhance your feeling, brings a new way to enjoy sake and is enjoyed as a toast.