This is a kind of mountain yam. It gets sticky when you grate it. It is rich in nutrients and it makes you energetic when you are tired.
“Imo-jiru” potato soup is how people in Kakegawa eat jinenjo. Grate jinenjo with its peel and mix it with mackerel soup and miso, then enjoy. You can mix it with rice.
Don’t get surprised if you hear someone slurping it down. It is OK to do that in Japan. This is a local food that you can eat only during winter.