The calculated distance (air line) between Hachiōji and Ōmihachiman is approximately 185 miles respectively 298 kilometers.
By car or train, the actual journey to Ōmihachiman is certainly longer, as only the direct route (as the crow flies) between Hachiōji and Ōmihachiman has been calculated here.
Air line (approximately)
298 kilometers
161 nautical miles