MOONSTONE's debut work follows Aisa Ryu who wakes up to find himself looking up at the sky in the rural village of Takachiho. He soon realizes he has no memory of his past. Confused, he is taken in by his cousin, Kittaka Sanae, and moves into the Tachibana family home, where he meets the four sisters. However, an incident in a neighboring town leads Aoi and the sisters into a series of ongoing murders in this suspense visual novel. Viewing all endings unlocks short stories for each heroine.