Trade between Japan and China developed at the beginning of the 15th Century under the rule of Yoshimitsu, the 3rd Shogun of the Muromachi Shogunate. This period of trade between the two countries was known as Nichi-Min or Kango trade. Ming China agreed to this trade on condition that Yoshimitsu brought the Japanese pirates called Wako under control. Hence, the Shogunate's trading ships all carried a Kango-fu identifying seal in order to distinguish them from the pirates. The players are traders in Sakai, a port in Osaka Prefecture. They are trying to earn money from importing goods to Japan from China. So the Kango-fu is very important to the success of their business.