In the 14th year of the Tenpo era, there was a secret shrine for “Bansha Aratamesho” (a research institution for foreign literature and learners) under the city of Edo. To the public, this organization was punishing the scholars who studied the Western Culture. However, this organization's true mission was far more significant. Bansha Aratamesho was responsible to slay the “Yoh-is”, the evil spirits with flesh and blood from another world, that were expanding into Edo.
Bansha Aratamesho is not an official organization. Members do not have the typical credentials to be the vassal of Shogun. It consists of a man who lost his memory, a man who was raised in a mountain and a girl who dresses up in a man’s outfit. Their special powers are yet to be known, but they all have special abilities that help slay the Yoh-is.
The code name given to them is – “Ayashi”. Ayashis collect all types of information that seems bizarre. With thorough investigation, they locate the Yoh-is and hunt them down.