Kamikochi to Shirakawa-go by bus?

I am planning to stay one night in Kamikochi (22 May 2024) and the following morning take a bus to Shirakawa-go.
If I am not mistaken I would need to change buses at Hirayu and Takayama.
Can I book bus tickets for all 3 legs of the journey to Shirakawa-go from the Kamikochi bus terminal itself?
Do I need to book the tickets in advance?
Also I could not find any bus schedules so I don't know when the earliest bus leaves from Kamikochi and what the frequency of buses is like at Hirayu and Takayama.
Thanks in advance!

From Kamikochi to Takayama:

At this time Nohi bus does not announce the timetable. I bought the ticket on site 2 years ago.

From Takayama to Shirakawago:

Timetable

https://www.nouhibus.co.jp/route_bus/takayama-shirakawago-line-en/#tim...

Red "R" means reservation required. You can reserve from here. Note that reservation starts one month before.

https://japanbusonline.com/en/CourseSearch/11900040002