Youzou Torii serves as the South Edo Magistrate and is the lord of Kai domain. A high-ranking shogunate official, he staunchly supports Chief Elder Mizuno Tadakuni's Tenpō Reforms and plays a key role in implementing these political and economic changes.

He maintains a specialized task force to combat supernatural threats. This group includes individuals such as Matsue Sote, a relative of his retainer Honjō Tatsusuke, who gained the ability to breed yōkai-like creatures after returning from the Other World. The Magistrate deploys these creatures as a task force against other yōkai.

His political maneuvers and actions are significant to the plot. He pursues his own agenda concerning the youi monsters and demonstrates particular interest in the protagonist, Ryūdō Yukiatsu, for reasons extending beyond his supernatural power. As a primary antagonist, he aims to harness the rampaging youi monsters for his own plans.

Within the shogunate government, he faces political opponents including Tōyama Kagemoto, the former North Edo Magistrate transferred to Chief Censor, and Atobe Yoshisuke, the biological brother of Mizuno Tadakuni who serves as Ogasawara's superior.