I'm a high school student. This summer, I'm visiting a small town in the country. The town is surrounded by mountains and people peacefully coexist with ayakashi here. I don't remember it, but I feel like there was something I cherished here. The people I spend my time with here all feel somehow important. They are Giou (an ayakashi), Shinonome, Shu, Takatora, and Chihaya. I get involved in trouble due to an appearance of another mysterious ayakashi. Mysterious phenomena... Nightmare... I don't wanna remember that thing, but I have to... When the moon becomes full, what will happen to me...? Now, my summer starts...