The calculated distance (air line) between Ōkuchi-shinohara and Ōita is approximately 99 miles respectively 159 kilometers.
By car or train, the actual journey to Ōita is certainly longer, as only the direct route (as the crow flies) between Ōkuchi-shinohara and Ōita has been calculated here.
Air line (approximately)
159 kilometers
86 nautical miles