The Asahi newspaper site reports on the first sake produced from Aomori Prefecture's special table rice Seiten no Hekireki (晴天の霹靂, "bolt from the blue").
The first brewer to turn this non-sake-specific rice into sake is local company Momokawa, who released their Seiten no Hekireki Momokawa daiginjō junmai on 4 April 2018.
It's expected to hit shops inside the prefecture on 10 April on sale for JPY 2,000 per 720 ml bottle, with only 1,600 bottles available this year. However, production is expected to increase to 10,000 bottles next season, and sales to expand to nationwide.
Seiten no Hekireki isn't a sake-specific rice, but the rice used for brewing was graded Special A by the Japan Grain Inspection Association (also known as KOKKEN). According to Momokawa's production department manager, Koizumi, this variety doesn't crack easily even when steamed and is full of characteristic rice umami. Momokawa used rice with a protein content of 6.4% or less (unpolished, with moisture content calculated as 15%) to minimise any zatsumi (雑味, "rough" flavours caused by unwanted elements such as protein or lipids in the rice raw material).
Company president Yūji Ueda visited the prefectural offices on 28 March to report on the project to prefectural governor Shingo Mimura. Ueda described the sake as having produced a daiginjō with a floral, rounded aroma and gentle rice-derived umami, while Mimura commented that the aroma was intense and the sake would go perfectly with another local speciality, hirame (Japanese flounder).
So, there you go. Sake does not have to be made from sake-specific rice, even ginjō and daiginjō. We had some amazing sake made from Tsuya Hime table rice when we visited the Gotō/Benten brewery in November 2017. (Gotō/Benten brewery visit part 1 | Gotō/Benten brewery visit part 2)