The calculated distance (air line) between Hitachi-Naka and Ryūgasaki is approximately 40 miles respectively 64 kilometers.
By car or train, the actual journey to Ryūgasaki is certainly longer, as only the direct route (as the crow flies) between Hitachi-Naka and Ryūgasaki has been calculated here.
Air line (approximately)
64 kilometers
34 nautical miles