Despite its appearance of stability, South Korea (hereafter Korea) faces a democratic crisis rooted in severe political conflicts. Korea’s democratic backsliding is different from that of Western European democracies. Rather than mainstream party convergence toward the center, Korea’s crisis results from extreme confrontation between mainstream parties and deep polarization in political and civil society. Why has Korea experienced polarization resulting in democratic backsliding? To address this question, this study focuses on key actors’ ideas of democracy, rather than socioeconomic, technological, or institutional explanations. It argues that Korea’s democracy is threatened by its supporters’ essentialist conception of democracy. As animosity between progressives and conservatives intensifies, each becomes increasingly entrenched and demonizes the other, revealing Korea’s democracy to be insufficient to resolve polarization and achieve national integration.