Yu douhu is tofu in boiled water.
Yu = hot water
dofu = tofu
Japanese foods have variety of foods that use soy beans.
For example, natto, soy sauce, tofu, miso and so on.
Historycally, Japanese people did not have eat meat because
Buddhism did not allow to eat meat. Soy beans was very important
foods to take protein.
(But I really don't know the history of yudofu.)
Usually, you put on ponzu when you eat yudofu.
Ponzu is a sauce containing soy sauce and vinegar or citrus juice.
Now it is getting colder in Japan.(But I guess Europe is much more
colder than here.^ ^ ; )
It is good season of yudofu now in Japan.