Mountain yam (yamaimo)
Translated as mountain (yama) potato (imo) these beauties have a long history in China, Korea and at least from the Stone Age in Japan.
They are fantastic as tempura and I love them raw as above with perhaps some soy sauce, ponzu or katsuobushi for a kick. The Japanese enjoy slimy texture and so the most common way to enjoy the yam here is grated which results in a slimy glutinous paste that is a beautiful experience once you get into it and tastes way better than it sounds!
You can get creative with it of course but it should be enjoyed grated at least once as it resembles almost nothing in the western culinary lexicon.