Takayama to Kamikochi

Hi, I have a quick question about how to get to Kamikochi from Takayama via bus. I understand that there is no direct bus to the Kamikochi area and instead, the best route is to stop off at Hirayu Onsen and then take the bus to Kamikochi (or preferably Taisho Pond first). However, I am unsure how to book this in advance or even if I am able to (online). I have booked buses in the Gifu general area already so it is a little confusing as to how there aren't any clear reservation pages this time.

I'd appreciate it if someone could enlighten me :)

Reservations are not possible for the buses from Takayama to Hirayu and the buses from Hirayu to Kamikochi. It is first-come, first-board, and there is usually enough capacity.