This study examines the impact of sea level rise on shoreline erosion at convex and concave beaches. While previous studies based on Bruun's hypothesis primarily focused on straight coastlines, this research extends the analysis to incorporate the distinctive responses of different shoreline geometries. Using Sentinel-2 satellite imagery, long-term shoreline changes over a nine-year period were analyzed and compared for Gangneung Beach (convex) and Jangho Beach (concave) in South Korea. The findings indicate that convex beaches experience intensified erosion due to reduced wave refraction and increased curvature. In contrast, concave beaches show mitigated erosion as sediment loss decreases with rising sea levels. These results deepen our understanding of erosion dynamics associated with sea level rise and provide critical insights for coastal management and adaptation strategies.