This study was conducted to supplement discussions on the characteristics of Korea’s ultra-low fertility rate. We focused on the possibility that the internal and external vulnerabilities of the current youth generation could negatively affect their progression to key life stages, such as marriage and childbirth. We also considered how the rapid decline in fertility rates may be linked to increasingly individual-level disparities caused by the polarization of social structures and various forms of inequality compared to older generations. Furthermore, we determined that these issues are closely related to the broader social instability currently recognized as a pressing concern in Korea.