The imagery in a Japanese person’s head and the imagery in an American’s head will be very different when bringing up the word “sweet potato”.
In America, sweet potatoes for the most part are available as “yams”, a potato with orange-brown skin and very orange flesh. In Japan, sweet potatoes have a purple skin with pale yellow flesh that deepens in color when cooked. It is called satsumaimo. And although I have seen satsumaimo potatoes being sold in American grocery stores, I have never seen yams being sold in Japan. Not in Tokyo anyways.
There are also purple yams, which are relatively popular in Japan. You will occasionally find sweets and snacks like Kit Kats and potato chips being sold in this flavor, although I have strangely enough never seen the actual potato being sold anywhere.
100 grams of orange yams contain 118 calories, 28 grams of carbohydrates, 4.1 grams of fiber, 1.5 grams of protein, and 0.2 grams of fat. 100 grams of Japanese satsumaimo contain about the same amount of calories and macronutrients. The Japanese love eating baked sweet potato, and have made many dishes using this tuber.
Satsumaimo tempura and Daigaku Imo are just 2 popular dishes with satsumaimo as the main ingredient. Satsumaimo tempura is this sweet potato sliced into thin pieces, dipped in batter, and deep fried. It is usually eaten with other vegetable tempura. Daigaku imo, which literally means “college potato”, is satsumaimo in its candied form sprinkled with some black sesame seeds. This dish was invented to provide a sweet dessert at an affordable price for college students who could not afford other kinds of sweets. It is loved by people of all ages today.
You will often see roasters in supermarkets and grocery stores, with fresh baked sweet potatoes when you go to Japan. If you are in the right place at the right time, you will also find a white van driving around your area, with a megaphone constantly playing a baked sweet potato jingle as the driver of the van goes around trying to sell his delights.