For Sumi-E and Japanese Calligraphy, you will also need a felt mat to paint on.
Black or green felt mat (or any colors) is used for calligraphy but white mat is used for Sumi-E paintings. The reasons for using different color mat is because in Sumi-E painting you need to see the color well. With black mat on the bottom, the thin rice paper tends to show through the mat color. So, it’s better to use a white mat to be able to see the delicate color while painting.
The felt mat also protects your table or desk surface from getting wet with Sumi or water, and prevents the wet paper from sticking to the table, and prevents the paper from moving during painting.
You can also find grid painted mats and they are very useful for practicing.