In the travel industry, there is a term for Japan called the Golden Route. It basically means the popular travel route of travellers from Tokyo, Kyoto and Osaka or vice versa. The reason why this is a common route for travellers to Japan is because there are three major international airports (Haneda, Narita and Kansai Airport) connecting two major cities, Tokyo and Osaka for international travellers to fly into. Plus, the Shinkansen connects all three cities, making it a kill three birds in one situation for tourists.
But as a result, overcrowding and an influx of tourists to these areas has become prevalent. To combat this, Japanese airlines like ANA has introduced discounted or complimentary domestic flights to other parts of Japan when booked with your international flights. I have used this service quite a few times to travel to Sapporo, Okinawa and Nagoya and I will share that it was very convenient for jetting across the country without having to touchdown in the major hubs.