As wave climates around the South Korean coasts are not predominated by a particular wave system, but rather supplied by multiple wind-wave systems, the assessment of the total wave power, an integration of the wave power over all frequencies and directions, is not helpful to wave energy converter technologies, which ideally operate within a narrow frequency-directional band. This study develops a new methodology for discerning wave energy hotspots for potential energy project sites and identifies dominant wave systems contributing large energy to the total wave power at each hotspot by analyzing frequency-directionally-temporally resolved joint wave power distributions. The joint distributions were computed using bulk wave parameters obtained from the most recent wave measurements ranging from 2008 to 2019. Three wind-wave systems, i.e., year-round northeasterly, southeasterly in summer, and northwesterly in winter, are the main energy suppliers, and determine resource attributes (e.g., frequency-directional spreading and seasonal variability) within the hotspots. This study demonstrates that the assessment of the dominant wave systems differs from that of the total wave power. While previous studies have highlighted the waters near Southern Jeju as a potential project site, having the largest total wave power, we observe that the wave system with a 6.0 – 7.0 s peak period from the NNE direction near Western Ulleung exhibits a higher energy density and a lower seasonal variability, which is a more desirable resource. The present study supports the scoping of energy projects and the optimization of wave energy conversion design targeting the dominant wave system and desirable resource conditions.