The calculated distance (air line) between Ōtsuki and Fujikawaguchiko is approximately 18 miles respectively 30 kilometers.
By car or train, the actual journey to Fujikawaguchiko is certainly longer, as only the direct route (as the crow flies) between Ōtsuki and Fujikawaguchiko has been calculated here.
Air line (approximately)
30 kilometers
16 nautical miles