The calculated distance (air line) between Gwangmyeong and Naesŏ is approximately 179 miles respectively 289 kilometers.
By car or train, the actual journey to Naesŏ is certainly longer, as only the direct route (as the crow flies) between Gwangmyeong and Naesŏ has been calculated here.
Air line (approximately)
289 kilometers
156 nautical miles