We review the literature to show why South Korea is witnessing a dramatic rise in young adults who opt into childless singlehood. We argue that social change occurred over a compressed amount of time in South Korea. Confucian familism and ideational factors specific to the Second Demographic Transition (SDT) coexist and collide. The demands of Confucian familism also tend to be incompatible with the socioeconomic realities facing young adults. Influenced by the ideational factors characterizing the SDT, young adults may feel that it is acceptable to forego marriage. However, due to the strong influence of Confucianism on the institution of marriage, they may perceive married life to be largely inflexible. Thus, when confronted with incompatibilities between married life and other life domains, growing shares of Korean young adults may avoid married life and opt for childless singlehood.