Disclaimer: it is not (very) hazardous to indulge in Daishinshu's sparkling sake. 
Although the brewery indeed cautions their customers, providing plenty of instructions on how to open it correctly. The brewery store sells ice picks to release the gas accumulated in the bottle (see the video above). Once you perforate the cap, the escaping gas will intermix the sake and the lees, turning its colour milky. We used the cork driver on a Swiss Army knife, which worked flawlessly. The bottle has a spare cap to be placed once the original cap is removed. (Believe me, you won't need it, as this is a sake you won't keep overnight.)
Daishinshu's sparkling sake is a sought-after product, as we could witness in the brewery store. It is slightly effervescent, mild and subdued in taste, with refreshing acidity. It has a citric flavour and is not sweet. Elegant and vivifying.
Although the brewery indeed cautions their customers, providing plenty of instructions on how to open it correctly. The brewery store sells ice picks to release the gas accumulated in the bottle (see the video above). Once you perforate the cap, the escaping gas will intermix the sake and the lees, turning its colour milky. We used the cork driver on a Swiss Army knife, which worked flawlessly. The bottle has a spare cap to be placed once the original cap is removed. (Believe me, you won't need it, as this is a sake you won't keep overnight.)Daishinshu's sparkling sake is a sought-after product, as we could witness in the brewery store. It is slightly effervescent, mild and subdued in taste, with refreshing acidity. It has a citric flavour and is not sweet. Elegant and vivifying.