Shirakawago to Kanazawa Reserved Bus

Hello!

We will be travelling to Shirakawago from Kanazawa this March. We booked return reserved bus tickets. My question is, if we decide to leave earlier than planned, may we get on a bus that's departing earlier than our reservation?

Thank you!

According to the website of Nohi Bus Company, there are reserved bus and non reserved bus.
If you would like to take earlier bus than the one you reserved, you should call them to cancel and reserve another one if the earlier one is reserved bus.
If the earlier one is non reserved bus, reservation is not required naturally, however you should notify them for cancellation in terms of waiting list.

https://www.nouhibus.co.jp/highwaybus/kanazawa_en/

They will not let you change at the bus station as they do not have the capability to change online bookings. The previous advice provided sounds the way to go.

there are reserved bus and non reserved bus.

That is not for your case.

Reservation is necessary for your ride of any bus running from or to Kanazawa on the route Kanazawa -- Shirakawa-go -- Takayama.

This bus route is operated jointly by Nohi Bus and Hokutetsu [Hokuriku Railroad].
You may see a Hokutetsu logo on the body of your bus.

- Japan Guide: Bus timetables for the routes via Shirakawa-go
https://www.japan-guide.com/bus/shirakawago.html

if we decide to leave earlier than planned, may we get on a bus that's departing earlier than our reservation?

You reserved your bus tickets through Japan Bus Online, didn't you?

Your reservation is only for that certain bus.
To take another bus, you should make a reservation specifically for it.

If you cancel your current bus tickets by the deadline (designated by the website),
you can avoid paying for the both.
A cancellation fee is required, whose amount seems to be 100 yen per ride per person.

- Japan Bus Online: Frequently asked questions
https://japanbusonline.com/en/FAQ
: Check the section "Cancellation Deadline" of this FAQ.