This study examines the investment behavior of Taiwanese banks following TSMC’s establishment of a semiconductor plant in Kumamoto, Japan. Situated within the framework of economic security and supply chain resilience, the research investigates how financial institutions respond to cross-border opportunities arising from the semiconductor industry’s transformation. Drawing upon in-depth interviews with senior executives from four major Taiwanese banks, the study integrates the theoretical perspectives of opportunity discovery, industrial networks and clustering effects, and institutional theory to analyze the strategic motivations underlying these investment decisions. The findings reveal three central characteristics of Taiwanese banks’ investment strategies: first, opportunity discovery and first-mover advantage, as banks exhibit strong market alertness, capitalizing on yen depreciation, government support, and supply chain restructuring to secure resource advantages and early market positions; second, industrial networks and clustering effects, where the globalization of the semiconductor supply chain and the geographic concentration of industries in Kyushu significantly influence investment orientations, enabling banks to deliver specialized cross-border financial solutions; and third, institutional stability, as Japan’s low institutional risk—characterized by political stability, transparent legal systems, and consistent economic policies—reduces operational uncertainty and facilitates financial innovation. This study contributes to understanding how Taiwanese banks leverage opportunity recognition, industrial integration, and institutional advantages to advance cross-border investment strategies. The results underscore the strategic role of the banking sector in strengthening supply chain resilience, enhancing Taiwan–Japan economic cooperation, and reinforcing regional economic security amid shifting geopolitical dynamics, while offering policy and managerial recommendations to promote continued financial innovation and sustainable regional collaboration.