In this fun chapter, our protagonists find themselves caught up in an adventure after Ruri decides to take them on a camping trip as part of the Geology Club; they discover a mysterious cave that could be dangerous, as there could be located a dark stone, Onigawara with Kagami get into the cave for catching the store but suddenly everything star falling down and we found Kagami , Ruri and Tandoji in real danger. How will they survive this? Find out for yourself.