The Japan Rail Pass (JR Pass) is by far the best and most popular train pass available. It covers the entire Japan Railways(JR) network including some buses and ferries. The Japan Rail Pass comes in 7, 14 and 21 consecutive days. Each of these Japan Rail Passes is available in Economy (Ordinary) and First (Green) Class as well as child and adult rates. Please note that Japan Rail Pass can be purchased outside of Japan.
The Japan Rail Pass (also commonly called JR Pass) is a very cost effective rail pass for long distance train travel in Japan. It can be used by foreign tourists only, and offers unlimited use of JR trains for one, two or three weeks at a cost that residents of Japan can only dream of.
The Japan Rail Pass must be purchased before your arrival to Japan, because it is not available for sale inside Japan. The pass comes in two types: ordinary and green car. The latter is valid on green cars (first class cars) that offer more spacious seats than ordinary cars.
Travelling to Japan isn’t cheap as the transportation fee takes up a big parentage of the total expenses.
Because Japan’s land shape is long and thin, normal return ticket costs JPY 29,440 (Approx NZ$439) even if you travel from Tokyo to Osaka. And the JR Pass Ordinary for 7days only cost JPY 29,650(Approx NZ$443).— as of Jan 2020.
So it is better to purchase a rail pass to travel around Japan.
Information source: japan-guide.com