You can find the schedule here at the bottom of this website but it's in Japanese. You want to look at your starting point which is the 3rd column from the right which says 十二湖駅前 (Juniko station) and your destination which is the very right column 奥十二湖駐車場 (Oku-Juniko parking lot).
http://www.konanbus.com/travel/junilake.html