Japan prefecture boundaries: piuccio/open-data-jp-prefectures-geojson (MIT, Fabio Crisci). Upstream: MLIT National Land Numerical Information administrative areas. https://github.com/piuccio/open-data-jp-prefectures-geojson
Simplified for discovery display on 2026-09-23. Small islets omitted; not for navigation or legal boundaries. Original license alongside this file.