The world of Long Summer is shrouded in eeriness. Every six days, on the seventh day, this strange entity invades the dream realm, releasing its malevolent forces to affect reality. On this particular day, an unusual murder case in Kuroki City leads to the discovery of a mysterious girl. She possesses the Eye of Truth, which allows her to see through illusions on the seventh day.

Reincarnated in the island nation of Japan as a Miko. All Shiramizu Aki ever wanted was to drift peacefully through life, but she slowly comes to realize that something about this world is fundamentally wrong.