I am Toma Hikaru, attending Izumo Gakuen High School alongside my sister-in-law Miyuki, childhood friend Nanami-chan, and rival Nagisa. Lately, I've been having vivid dreams of a stunning shrine maiden, diligently praying in a lake in the buff. I feel as though I may recognize her, but I'm not entirely sure. Additionally, my dreams have shown me a mysterious room within Izumo Gakuen, causing me unease. Despite my apprehension, I decide to explore the room, unwittingly setting sail on a lengthy journey.