Sake

[Dodge]

This is the site I'm using to make my sake

http://homebrewsake.com/home/recipe/

You will see that the koji and rice are added 12 hours apart. The first step - yeast mash is similar but this is where the yeast is added.

After that it's 12 hour steps adding koji then later the rice and water is added. It's pre prep stages as you said to allow the yeast to continually work when more food is available