
A vessel for holding hot water to drink after meals
What is yutou?
A yutou (湯桶 in Japanese) is a vessel with a handle and a spout that holds hot water to be served after meals. At soba restaurants, after you have finished eating Zaru Soba or Seiro Soba, yutou is served with soba-yu (hot water left over from boiling soba). In kaiseki cuisine, hot water is poured over the burnt rice left at the bottom of the rice cooker, and the rice is lightly salted and served in a yutou.

How to use
In the case of soba-yu (the water used to boil the soba), it is common to pour soba-yu from a yutou into the dipping sauce after finishing eating the soba. In kaiseki cuisine, a ladle-like tool called a yunoko sukui is used to scoop hot water from the yutou and pour it over the remaining mouthful of rice to make yuzuke. The yuzuke is eaten clean to the last drop, along with pickles and other vegetables.

Substitute for yutou: when you don’t have it
Any vessel with a spout, such as a teapot, can be used as a substitute.
Trivia
The traditional way to eat kaiseki cuisine is to save a bite of the rice served at the beginning of the meal, and then at the end of the meal, immerse it in hot water from a yutou to clean the bowl. This is said to come from Zen Buddhist dining etiquette. The reason for drinking soba-yu is thought to be to ensure that the flavor and nutrients that have been dissolved in the soba-yu are not left behind.