Well, things are getting clearer now: stay at a cheap lodge with smelly dudes or burn the credit card in a nice hotel, staying alone but hopping to get in touch with Japanese ladies...hum hum, as we say in french, "mon coeur balance" (literally "my heart is swinging", means I can't decide).
Creek boy - is it the Prince hotel you are talking about ? I'll check on their website but do you know how much would be a simple room for 7 nights ? Do they still have vacancy ?
Or another idea: arrive at Hirafu without any reservation, find a girl with a flat or hotel room and propose me as a human