Usucha is a thin, weak tea made from the powdery tea called Matcha in Japanese.
The Matcha used is made from leaves from tea bushes that are under 30 years old. The powder is traditionally stored in a container made of lacquerware called a "natsume."
There is a ceremony around how you drink it. It is made one bowl at a time. One person drinks the tea, then returns the bowl to the host, who washes and wipes it and makes more tea in it for another guest, and so on until everyone has had tea. The ceremony, though is formal times than that for Koi-Cha tea.
70ml (2 1/3 oz) water between 75-95 C (167 to 203 F.)
The tea and water are put in the tea bowl, then mixed with the tea, and whisked fairly rapidly. When whisked, it will be somewhat frothy at the top.
The cooler water temperature makes it possible to drink the tea in lacquerware cups without handles.