It’s a kind of yam cake made from Konjac yam, jelly-like texture. Konjac foods are good for your health because they’re no carb, high fiber foods. They also have lots calcium, kalium and minerals. Eat Yam as Konjaku is a unique culture, only exist in Japan. It is very chewy. Konjac has been known in Japan since the sixth century as a medicinal food, and it has been eaten for 1500 years. In 1846, the publication of the book Konnyaku Hyakusen (100 recipes of Konnyaku) demonstrates its popularity in the Edo period.
Nowadays Japanese ladies eat it as diet food.