To understand the impacts of past land-bridge formation and vegetation shift under Quaternary climate change across Sakhalin, Hokkaido, and Southern Kuril Islands (SHSK) in northeastern Asia, we investigated the demographic history of forest-dwelling marten species. We employed the multiplexed ISSR genotyping by sequencing (MIG-seq) method to obtain genome-wide Single Nucleotide Polymorphisms (SNPs). We tested possible scenarios of colonization and diversification of the SHSK sables with the Japanese marten as an outgroup.