<p>The Tsugaru Warm Current (TgWC), a component of the Japan Sea throughflow system, is driven by sea level differences across the Tsugaru Strait. Our findings revealed that sea level fluctuations at Fukaura, on the Japan Sea side of the strait, are correlated with the Pacific Decadal Oscillation (PDO), with a temporal lag of approximately 6.5&#xa0;years, particularly after 1999. Using ocean data assimilation reanalysis products, we located where this large correlation originated in the upstream region of the TgWC; we found similar correlations with a lag between the PDO and sea surface height over a wide area, including the central Japan Sea and the Kuroshio region. Through empirical orthogonal function analysis of the northward flow over the East China Sea continental shelf, we confirmed that its first and second modes were significantly correlated with the PDO and the PDO with a 6.5-year lag, respectively. The latter was presumed to be caused by baroclinic Rossby waves in the Pacific. During the negative phase of the PDO from 1999 to 2012, a shoreward shift in the Kuroshio in the East China Sea, associated with the combined effects of the positive delayed PDO, brought lighter water to the Japan Sea more efficiently. This advection scheme including light water from the lower latitudes is closely linked to the meandering of the Kuroshio and the bifurcation of the Tsushima Warm Current in the Japan Sea via the torque balance of the Japan Sea throughflow system and can change the volume transport of the TgWC. </p>