Sake Brewing in Shrines and Temples
Sake World Newsletter Issue #75
Sake Brewing in Shrines and Temples
http://www.esake.com/Knowledge/Newsletter/SW/SW2006/sw2006_0.html
There is a reason Mushin has a constant supply, he probably makes it himself.
In addition to the history of Sake brewing there are some interesting tidbits about the interaction between Buddhist monks and Shinto priests. At one point they happily shared temples as well as the results of their brewing.