 Once, Chen Shubao was impressed with an essay Yu wrote on historical uses of the military and he awarded Yu a horse.In 589, Chen was conquered by Sui Dynasty, and Yu subsequently served in Sui's legislative bureau (內史省, "Neishi Sheng") as a low-level official during the reign of Emperor Wen.Despite his position, however, he had little money, and he was forced to take retainers in writing calligraphy in order to support his parent(s).