Do all buses from Kosoku Kakamigahara to Shirakawa-go require a reservation beforehand?

We’re exchange students staying in Gifu for a couple of weeks and mostly relying on cash. We plan to visit Shirakawago on 24 Dec 2022 (next weekend) and are planning to take a bus from Kokosu Kakamigahara to the Shirakawago bus station.

Google Maps doesn’t offer any information about the bus we plan to take beyond the route/fare. Buses we’ve found online, such as Willer and Gifu bus, require a prior reservation through credit card payment. We would like to avoid paying through card due to difficulties in processing international refunds etc. (we have mostly stuck to cash throughout this short trip). Calling ahead is not very helpful as the operators refused to make cash reservations when we tried.

Is it possible to find a bus that does not require a reservation and is around the same fare (~4000 JPY)?

Thanks!

Thanks in advance!