Hello there, I see you said you took a shuttle to the onsen? Does the onsen send it for free to one of the train stations over there? If you remember can you let me know? We're trying to see if it's accessible for 8 adults with jr rail passes.
Agreeing with Alex.
Guests that are spending the night there can also book the curtesy shuttle for pick up at Jomo-Kogen station. You can get to Jomo-Kogen by Shinkansen using the JR pass.
The courtesy shuttle came in the afternoon, around check-in time, so I’m not sure how practical it would be for you if you are planning a day trip...
They only pick you up if you reserved a room and sleep over. For a day trip they don't pick you up.
In October I did a day trip.
You can't use the JR the whole trip.
You can use the JR pass till Jomo-Kogen station. Out side the station you can go to the Tourist information office. There you can buy a ticket for the onsen that includes local bus and return to Jomo-Kogen station.
Last bus goes back around 16:45.
Get an answer from Takaragawa Onsen Osenkaku staff and past guests.