This is a very interesting chance! Fukuoka’s Mori no Kura offers a Funagumi junmai, which means that it’s pressed in a traditional top-pressure tank, called a “fune” (boat) and bottled by hand directly from the press. Naturally, that means it’s also a muroka genshu.
The fun thing here is that I have one that was “matured” for a summer and sold in the fall, and one that is fresh pressed.
These sakes are not made in exactly the same way (they use different yeast, for example), but there are enough similarities to show how sakes develop with a bit of aging.
I actually had the aged version first. As a Fukuoka sake, I expected it to be more full bodied and sweeter than, say, a Fukushima sake, and this is true. However, rather than calling this a “sweet” sake, I’d place it more on the umai-range. It had a big boldness to it that lingered, which was bolstered by some astringency. There is very little acidity to it, as well.
This strikes me as a focus sake, meaning it’s not very well geared towards mealtimes. The boldness tends to over power, and draws the attention to itself. This isn’t a bad thing, but it can also be a bit oppressive in, say, a social drinking session.
On the other hand, the fresher version was a great meal sake. This one was bottled in December of 2019, and drunk in early February, so it’s not exactly straight from the tank. At the same time, it had more of the delicacy of a shinshu. There was still a full bodied sweetness to it, but it was more balanced toward the lighter side, with less umami. It was a much more meal-friendly sake than the matured one, because it was less assertive.
This jibes with the general wisdom that aging sake primarily builds umami, and creates more complexity of flavor.