Kurosengoku is a very rare black soybean cultivar. About 30 years ago, its cultivation was stopped because it required great care to cultivate. In 2001, the cultivation was started again in Hokkaido, but still its production accounts for 0.2% in Japanese soybean production. Because the bean is much smaller than regular soybean, same weight Kurosengoku contains more skin compared to normal sized soybean - the black skin part contains anthocyanin, isoflavone and polyphenol.
Put 1 tablespoon full of black soybean tea into a mug cup and pour hot water into the mug. Enjoy the tea after 3-5 minutes. The used soybean can be eaten as it is, with honey, with salad, etc. (Please eat used soybean in the same day or next day (if kept in a fridge).
FOR A FAMILY
Put 2 teaspoon full of black soybean tea in a teapot, pour 300 cc (10.2 fl oz) of hot water into the pot. Wait for 3 minutes and the tea is ready!