Very little is known about Oriya. He owns Kou Kaku Rou, an elegant traditional restaurant that is secretly a brothel for the rich and powerful. This, he inherited from his family, who has held Kou Kaku Rou for many generations (it is described in the manga as one of the oldest, if not the oldest restaurant in Kyoto). He is a friend of Muraki's from college, and Muraki's only known friend. He wears a very distinctive and ornate kimono. He is often seen smoking a traditional Japanese kiseru pipe and practicing kendo. He is an expert with the katana. He has very strong feelings toward Muraki, though it is unclear whether his feelings are specifically romantic or not. In the most recent continuation of the series, he is shown to be hosting and caring for Ukyou, Muraki's childhood sweetheart.

Though he is usually seen as a neutral or sympathetic figure in the story, he is also an active collaborator of Muraki's. He has helped Muraki cover up his murders through his network of high-ranking officials, and in return, Muraki has disposed of troublesome elements among the women of his brothel.