The calculated distance (air line) between Kitakyushu and Kokubu-matsuki is approximately 146 miles respectively 236 kilometers.
By car or train, the actual journey to Kokubu-matsuki is certainly longer, as only the direct route (as the crow flies) between Kitakyushu and Kokubu-matsuki has been calculated here.
Air line (approximately)
236 kilometers
127 nautical miles