Mount Ishizuchi

Ishizuchi Fureai-no-Sato
1-25-1 Nakaoku, Saijo-shi
0897-59-0203
Comfortable and well-equipped cabins from ¥2920 for 2; basic rooms starting at ¥1170 per head, and riverside camping space (on gravel) at ¥200/person

An excellent place to stay, only 10 minutes down the road with a bus stop nearby. There is a little restaurant on grounds, bathing facilities with an ofuro public bath, and barbecue pits. Note that this is really geared for larger groups, so call ahead to reserve and make sure the place is open and not filled with grade schoolers.

Chōjō-sansō
0897-55-4168
A night in fairly spartan accommodations with two meals will cost ¥8500

The name is Japanese for "summit mountain lodge", an apt description of this mountain hut run by the temple. It's open from early May to early November. Note that you will be expected to take all your garbage down with you.