Originally Posted by
joejones
There are some limited cases where JR allows backtracking, but only when the passenger is on a train that passes through their destination station without stopping, and even then it's only allowed for certain stations (e.g. you can backtrack from Shinjuku to Yoyogi, but not from Shinjuku to Shin-Okubo).
https://www.jreast.co.jp/kippu/1105.html
Off topic... but this explains a lot when I was in Hokkaido.
I was trying to get from Akkeshi - Abashiri and the JR agent said it would be cheaper if I either got off at Higashi Kushiro and changed trains or rode all the way to Kushiro but I couldn't exit at the station. It's the backtrack segment that it I wouldn't be charged in the latter's case.
I ended up paying a few hundred yen more for two tickets Akkeshi - Kushiro and Kushiro - Abashiri so I could exit the platform to buy some food and stuff in Kushiro since it was almost a 2 hour wait followed by a second 3 hour train ride.