Antitrust law is relatively new concept of contemporary Far Eastern law. Ancient Chinese tradition was based on administrative guidance if trade.
In Japan, military rulers did not care about business and trade was thus managed by associations of businessmen. After World War II, Americans brought their antitrust model to Japan.
The People's Republic of China due to its WTO's membership as from 2001 had to implement antitrust legislation as well. They decided for the EU system of competition law.
It is important to follow not only legal norms of antitrust law in both countries but particularly its judicial interpretation. The latter may lead to substantial differences between US or EU model and reality in Japan or China.