Bus route to Shirakawago

Hi, I currently stay in Awaji area. I plan to go to Shirakawago after that, I wonder if there's bus to Shirakawago from this departure bus option:

- Maiko
- Sannomiya
- Shin-Kobe
- Osaka

If there is, do I need to book ticket first? Or can I buy it with cash directly on the bus.

Or is there better route to reach the Shirakawago from Awaji. Thank you.

Only from "Osaka" no operate fromo Kobe area.
Bus(need booking) is bellow but operate numbers not enough.
http://www.nouhibus.co.jp/english/kyoto_osaka.html

This "Osaka" means from Osaka ekimae (front of JR Osaka station)
/Higashi Umedacity (near city subway Higashi Umeda stn's exit closer than JR Osaka).
http://willerexpress.com/st/3/en/pc/bus/uketsuke/detail.php?k=550&key=...
Bus stop no ticket office/window with only bus driver
so cannot buy dep time as no booking if enough cash.
(booking limit until 15min before dep)

If by trains use HyperDia input from ShinKobe,Kobe or Sannomiya to Takayama.
http://www.hyperdia.com/en/ (Shinkobe is Shinkansen station)
(LtdExp Hida from JR Osaka no need transfer until Takayama but operate numbers not enough)
Then take reguar bus(no book) from Takayama Nohi Bus Center near Takayama stn.
http://www.nouhibus.co.jp/english/shirakawago_kanazawa.html
http://willerexpress.com/st/3/en/pc/bus/uketsuke/detail.php?k=413&key=...

Google MAP easier as route finder by train but setting items not good like HyperDia.
(HyperDia don't provide route map as result with)
https://goo.gl/maps/EPfwbVjBgfo (by car/not by bus)
https://goo.gl/maps/HrNhb6fxEbS2 (by train)