[itsthejb]

It’s possible the last train simply parks there for the night. This would mean that you ride the same train back after this misadventure

[Kwpolska]

That would mean the train driver spends the night in the middle of nowhere, I doubt they would agree to that.

[iggldiggl]

Otsuki might still be an booking-on/-off point for train drivers, with a number of drivers based there and regularly starting and ending their turns at that station and presumably living nearby. Or alternatively the train company finds it more convenient ferrying the driver with a taxi or company car to from the regular booking-on/-off point.