The basin of the Sea of Japan is the most studied area in the northwestern Pacific from the viewpoint of both Holocene climate and archaeological evidence. Therefore, this chapter provides an analytical review of mid-Holocene changes in climate and cultural dynamics, focusing on the regions of the Russian Far East, Japan, and Korea. It presents an investigation study spanning the interval from 8000 to 3000 yr BP. The first warming of the mid-Holocene took place between 7200 and 6200 14C yr BP in Sakhalin, although the maximum warming was between 5000 and 6000 14C yr BP. In Japan, taking into account information on the maximum high stand of the sea level, the peak of warmth appears to have been ca. 6500–5500 or 6500–5000 14C yr BP, although other evidence suggests the warmest stage in Japan was between ca. 8000 and 6000 14C yr BP. The Tsushima Current’s inflow in the Sea of Japan started after 9000–9500 14C yr BP, but the full-scale influx of the current might occur approximately 8000 14C yr BP. Following this account, the study reviews mid-Holocene climatic/paleogeographical changes, cultural dynamics, and their relations in the basin of the Sea of Japan. The main cultural changes in the Japan Sea basin correspond to the period after the climatic optimum of the Holocene. This chapter concludes by reinforcing the need for further investigation of the dynamics of climate and culture in the mid-Holocene.