The calculated distance (air line) between Haibara-akanedai and Okayama is approximately 115 miles respectively 185 kilometers.
By car or train, the actual journey to Okayama is certainly longer, as only the direct route (as the crow flies) between Haibara-akanedai and Okayama has been calculated here.
Air line (approximately)
185 kilometers
100 nautical miles