Wiki (in Japanese)
祖谷渓 - Wikipedia
One of the hotels (having English Page)
祖谷温泉で宿泊するなら秘境祖谷渓の一軒宿 ホテル祖 谷温泉
I have found no official sight seeing site but a tourist guide site.
OBOKE/IYA TOURIST NAVIGATION【sightseeing map】
Contact Miyoshi City Office of Tourism
Phone +81-883-72-7620