Dioscorea japonica (yamaimo, Japanese mountain yam) is a type of yam (Dioscorea) native to Japan (including Ryukyu and Bonin Islands), Korea, China (including ******), and Assam.
Dioscorea japonica is used for food. Jinenjo, also called wild yam is related variety of Japanese yam that is used as an ingredient in soba noodles.