Yuzu is a citrus fruit indigenous to Japan. It is 
about the size of a medium sized orange, but its skin has a slight yellowish hue. The fruit is pale cream in color. While the skin is wonderfully aromatic, the fruit itself is so bitter as to be nearly inedible. The skin can be found floating in ofuros at nicer ryokan or spas this time of year. It is also common to use the zest as a garnish.
The juice, despite being bitter, is extracted and stored for later use. The yuzu juice is often combined with two other indigenous and bitter citrus fruits, soy and sugar to make a multipurpose brightly aromatic, mildly acidic, slightly salty, slightly sweet sauce called ponzu.
Ponzu is frequently used as a dipping sauce for vegetables, and when combined with some finely grated daikon – large white radish – makes a lovely complement to meat for grilled meat.