The calculated distance (air line) between Hamamatsu and Minamiuonuma is approximately 177 miles respectively 284 kilometers.
By car or train, the actual journey to Minamiuonuma is certainly longer, as only the direct route (as the crow flies) between Hamamatsu and Minamiuonuma has been calculated here.
Air line (approximately)
284 kilometers
153 nautical miles