Hozaburo Ogasawara is a twenty-year-old scholar specializing in Rangaku, or Western studies. He serves as the leader of the Ayashi, a specialized unit tasked with combating supernatural entities known as Youi. The group operates under the public guise of the Bansha Aratamesho, an organization officially dedicated to the study of foreign texts.

In his role, Ogasawara must balance his responsibilities leading the Ayashi against the complex political machinations of the government, navigating the demands of his superiors while managing the team's missions against supernatural threats.