The RIKEN-led whole-genome sequencing of 3,200 individuals across seven Japanese regions, published in peer-reviewed Science Advances, confirms a tripartite model by isolating Emishi-linked northeastern ancestry that peaks in Tohoku and declines westward, distinct from both Jomon hunter-gatherer signals strongest in Okinawa (28.5%) and Han Chinese admixture dominant in western Honshu (13.4% Jomon). This fine-scale structure, derived from rare variant clustering rather than microarray imputation, exposes Japan's underappreciated internal diversity, contradicting decades of homogeneity assumptions rooted in small-sample studies. The JEWEL database integration with clinical data further links these ancestries to modern disease patterns, a dimension absent from the 2021 ancient-DNA papers that first floated the Kofun-era third wave. Broader East Asian parallels emerge when juxtaposed with Korean and Siberian ancient genomes: similar northeastern pulses appear in Ainu and Amur River populations, suggesting coordinated post-LGM demographic expansions missed by the original ScienceDaily framing. Limitations include reliance on modern samples without direct ancient DNA corroboration for the Emishi component and potential ascertainment bias in rare-variant detection; nevertheless, the 3,000-fold data increase over prior arrays yields robust geographic clustering that precision-medicine initiatives in Asia can no longer ignore.