The division of the Association of Southeast Asian Nations (ASEAN) member states in South China Sea disputes brings up the question of how state coalitions form. Analysis of this issue often delves into specific factors such as the legality of territorial claims and each state's military and economic power. Generalized predictions of coalitions, however, require analysis of a variety of factors that coherently fit together. An agent-based model is proposed here using landscape theory and the Interstate Tension Model. Test runs capturing the empirical reality of 2015 and addressing potential Chinese policy shifts to territorial concession and promotion of economic ties with other states were conducted to explore the plausible coalition formation between China and 10 ASEAN member states. The results match empirical reality, while some inconsistencies invite further investigation.