Yudofu (Yu Tofu) is Tofu cooked in hot water (Yu) in a pot. It is a very simple Nabe hot pot dish. Usually the hot water is not actually just water but Kombu (dried kelp) broth to give the dish more flavor. It is typically served with tangy Ponzu sauce for dipping. You can use Mentsuyu instead for dipping sauce if you don’t like Ponzu.
Mizutaki (水炊き) is a kind of hot pot dish (called Nabemono or simply Nabe) in which fish or other kinds of meat and vegetables are cooked in unseasoned fish broth and dipped in tangy Ponzu sauce. It is cooked in a ceramic pot called Donabe, right at the dinner table using a portable gas stove and we eat it as we cook. It is somewhat similar to Sukiyaki. But Mizutaki is an even more perfect food for cold weather.