The samurai training series of Mr. Hidehiko Matsumoto of Sawaya Matsumoto.
It's amazingly sappy and refreshing, a cross between the sappiness of Hana no Aka and the sappiness of Matsumoto!
The alcohol content is low, so it's easy to drink.
It has a slight effervescence, sweetness from the rice, and a refreshing acidity.
It's a very rare sake, but I happened to be able to buy it, so I was very lucky!