The term double diamond Fuji refers to this event and its reflection caught in a body of water in the foreground. This happens around April 20 and August 20 of every year (give or take a few days) at Lake Tanuki.
This is a great story, and it really speaks well of the kind of patience you sometimes have to exercise to get a really good shot. Not just the picture of the Double Diamond Fuji, but all the photos in this story are well worth a look.
I'm a sucker for really good photography, and this is remarkable.