score:3
I queried this with the hotel directly (should have done this earlier), and they responded as follows:
I’ll tell you the way to get here from Matsumoto. It takes 2 hours from Matsumoto Station to here by bus. You get the bus bound for Takayama bus terminal, get off the Hirayu-Onsen bus terminal, transfer to Shinhotaka line, get off the "Shinhotaka Onsenguchi (code H55)" bus stop, go straight up five minutes walk towards the direction of the bus, you can find our hotel on the left side.
The bus departs from Matsumoto bus terminal at 10:00 11:05 13:05 14:05 17:05. The 17:05 bus is the last one for Takayama.
Besides it takes 30 minutes from Hirayu to Shinhotaka-Onsenguchi bus stop. The bus departs from Hirayu Onsen bus terminal at (13:40 14:40 15:40 16:40 17:40 18:40 19:40).
It costs 3050 yen in total per person from Matsumoto to Shinhotaka-Onsenguchi bus stop.
The Alpico schedule from Matsumoto to Hirayu is available here: https://www.alpico.co.jp/en/timetable/matsumoto/r-takayama-matsumoto/
The Nouhi schedule from Hirayu to Kazeya is available here: https://www.nouhibus.co.jp/route_bus/shinhotaka-line-en/
Upvote:4
Kazeya is in Shin-Hotaka, and Nohi Bus appears to have a direct service from Matsumoto to Shin-Hotaka; unfortunately it runs for only a few days around New Year's. The rest of the time, you'll need to change buses at Hirayu (平湯温泉) to Shin-Hotaka Ropeway (新穂高ロープウェイ). (Schedule here: the connecting bus starts from Toyama, on the Japan Sea coast.)
Unfortunately, while it appears this bus runs past your hotel, it does not stop and the nearest stop, Shin-Hotaka Ropeway, is a few km down the road. You might be able to convince the driver to drop you off, but I wouldn't count on it, and flagging the bus on the return trip will be even harder.
The good news is that most Japanese onsen ryokan in remote locales offer a pickup/dropoff service from the nearest bus/train station, either for free or a small fee, so I would advise you to contact them directly.
That said, having visited the area myself, I would advise you to seriously consider renting a car. Public transport in this neck of the woods is very limited, making it tough to actually visit any nearby attractions, and the ¥5,760 return bus ticket will likely pay for a day's rental.
Updated following sage advice from fkraeim, whose Japanese bus schedule parsing skills clearly put mine to shame.