The case begins with the protagonist, who has lost his memory, waking up in a mountain forest where autumn leaves are flourishing.
She is rescued by a high school girl who calls herself "Taihouin Izuna", and is informed that he is in Momoshiro Village, a small village deep in the mountains of A Prefecture.

Who am I? Why did I come to this remote village? Why did I lose my memory? As the protagonist unravels her memories together with Izuna, she becomes embroiled in an inheritance problem that swirls around the village....