We took the Nohi bus from Toyama to Hirayu Onsen. Alternatively we could take the train to Takayama then take a bus to Hirayu Onsen. Somehow this Nohi bus look like a regular bus with no Nohi signage, boarding at Station 5 @ JR Station around 7.50AM, payment is made when we get off (no prior booking is required).
The journey is around 2 hours, but it's a fairly interesting route as we traverse through gorges which look like the Kurobe Gorge.
It took us an hour of walking to reach Myojin (our accommodation of the night), and the owner speak decent English. He advice us on the routes and ask us to get going at 6AM. Breakfast is at 7AM, but we could order our breakfast as lunchbox the night before.
Myojin might not be the best base for hiking as Yooko (the last base) is 2 hours away. Most tracks start from Yooko, and the 2-way between Myojin-Yooko already cost us 4 hours. If you plan to stay at Yooko, do bring along less luggage as it's 3 hours walk from the entrance of Kamikochi (the bus terminal).
There are plenty of mountain huts to choose from, so you can stay on top of the mountains. I believe prebooking is required, and it is seasonal. Maps and information can be obtain at the Information Center at the entrance of Kamikochi.