Against the backdrop of accelerating closures of childcare centers and kindergartens driven by South Korea’s declining birth rate, this study reconceptualizes childcare as an essential service for child development and proposes institutional and spatial design principles to ensure practical accessibility for all children, regardless of where they live. The analysis shows that although South Korea has built a largely universal childcare framework through initiatives such as free childcare, it still lacks a legal mechanism that guarantees effective access and utilization as a fundamental right. Demographic decline has followed an overall process of sparsification, marked by both the contraction of residential areas and an equalizing downward shift in density; however, it also exhibits distinct regional transition paths―for example, density dilution in metropolitan areas and clustered concentration in nonmetropolitan regions. Empirically, these dynamics appear as six types of spatial change and increasingly heterogeneous inequality patterns, shaped by regional urban structure and stages of development. To address this crisis, we apply a unique-coverage algorithm to identify and map irreplaceable “essential hubs” where a service void would emerge immediately if a facility were to close. Focus group interviews with facility directors and parents reveal a vicious cycle in which the erosion of childcare infrastructure undermines local living conditions and intensifies migration intentions among young adults; they also underscore deepening childcare inequities in sparse areas, where children face both restricted mobility and limited service alternatives. Ultimately, a transition toward a rights-based system that guarantees childcare access requires an integrated policy package: (1) codifying childcare accessibility as a legal right with clear remedial procedures, (2) introducing flexible public childcare models suited to low-density areas, (3) providing targeted fiscal support for vulnerable zones based on actual travel distance rather than administrative boundaries, (4) strengthening public transportation to secure mobility, and (5) implementing systematic closure management to ensure continuity of care.