In the early 1590s, the relative backwater of Hizen Nagoya in Kyushu was transformed into the launch pad for Toyotomi Hideyoshi’s East Asian War with the construction of a large castle and over 150 daimyo encampments. Hizen Nagoya was a relatively short-lived, dynamic, military-civil hybrid settlement. It thrived for a mere seven years before defeat in Korea led to its virtual abandonment. After the war, the castle was deconstructed and partly recycled, the encampments dismantled and the merchants dispersed, leaving behind few physical remnants but powerful memories. Unlike other symbolically important Toyotomi castles, it was never reconstructed. During the Edo period, Hizen Nagoya lost its strategic significance, political influence and economic dynamism. It was a melting pot that brought together cultural practices from distant Japanese regions (and beyond), before disseminating them across the archipelago via the returning soldiers. The East Asian War left not only a legacy of death and destruction, but also one of cultural creation, refinement and diffusion. The castle ruins are now a museum dedicated to historical understanding and Japan–Korea reconciliation. Its legacy has been overshadowed by that of the East Asian War and Toyotomi Hideyoshi but Hizen Nagoya’s contribution to the war and modern reconciliation efforts should not be overlooked.