This paper aims to explain how distinct political cultures have complicated China-Japan relations. Firstly, it illustrates the Chinese and Japanese political cultures on the basis of a sociological literature and first-hand observation of the author. Then, it analyses a case and an issue, that is, their negotiation for the 1972 Joint Communique and the struggle over the maritime disputes in the South China Sea in 2010. This analysis situates empirical events against the backdrop of each of the people's behavior rationale, thereby surfacing a deep political cultural variable. China's legal pragmatism and Japan's communal sensitivity are specifically relevant in these controversies. Together, they represent an epistemological difference, rendering meaningful communication difficult between the two people.