The calculated distance (air line) between Sinsang-ni and Kaesŏng is approximately 125 miles respectively 201 kilometers.
By car or train, the actual journey to Kaesŏng is certainly longer, as only the direct route (as the crow flies) between Sinsang-ni and Kaesŏng has been calculated here.
Air line (approximately)
201 kilometers
108 nautical miles