There are two ways to make warmed sake. The first way is used in professional establishments such as restaurants. The second method is recommended for very busy restaurants or to people who want to enjoy warmed sake at home.

WHAT IS NIGORI?

Nigorizake is made from moromi that is filtered through rough cloth right before fermentation is complete. In nigori, the sweetness of the rice is easily tasted. Some nigoris are of the sparkling variety because when nigori is done pre-fermenting, the carbonation remains.
WHAT IS GENSHU? - Genshu is raw, undiluted sake It is moromi that is heated, filtered, and has no added water. It is then bottled immediately. Genshu has an alcohol content of 20-22%. Most of the sake to hit the consumer market is not genshu. The sake has water added reducing the actual content to 15-16%.

The Yayoi Era (B.C.300~ A.D.300)

Sake is offered to the Gods as a gift

The keywords associated with Japanese sake are 'Rice' and 'Farming'. It is well known that the first Japanese sake was created in the Western part of Japan in the Yayoi Era when the hunting society changed to an agrarian society.
At the time, people had not mastered the technique of fermenting rice, so they had to chew the rice well, using their saliva in lieu of the modern fermentation process. Don't worry, though; this saliva-made sake was used solely for religious rituals, not as a beverage.
Not everyone could make the chewed sake Women known as Miko who serve god were the only ones qualified to make the sake intended for honoring the gods.
Currently tojis are nearly all men, but originally sake was made by women.