I picked up some lovely Japanese sweet potatoes at the market the other day. The Japanese variety are a deep red on the outside and yellow inside, with almost a slight chestnut-like flavour. In Japan, they are not only used in savory dishes, but are also baked, candied, dried, mashed, ground into flour, etc., and then used in all sorts of sweets.
I have heard of a very traditional style of using sweet potatoes, where people would dice them up and put them in the rice cooker along with their rice. The potatoes get perfectly steamed and the rice is infused with just a mild sweetness. I tried it out for the first time, and I absolutely love this! I also sprinkled on some sesame seeds for extra flavour.
For fun, here are just some of the creative ways that sweet potatoes and purple Okinawan sweet potatoes are used in confectioneries in Japan. They can be mashed into a paste, baked inside a thin layer of sweet dough, and then coated with cinnamon. Or, they can even be baked into little muffins! I have also seen them used in custards, rice crackers, and whipped up into a sort of sweet potato icing. But anyways, I definitely recommend trying out the rice!