My name is Toma Hikaru. I am attending Izumo Gakuen High School alongside Miyuki, my sister-in-law; Nanami-chan, my childhood friend; and Nagisa, who views me as a rival. I have started having a strange dream about a beautiful shrine maiden praying naked in a lake. I wonder who she is; I feel like I know her... I also see a strange room at Izumo Gakuen in my dream. Feeling uneasy, I decide to sneak into the room, unaware that it marks the beginning of a long journey.