Very little is known about Oriya. He owns Kou Kaku Rou, an elegant traditional restaurant that secretly functions as a brothel catering to the rich and powerful. This establishment has been in his family for many generations, described in the manga as one of Kyoto's oldest restaurants, if not the very oldest. Oriya is a college friend of Muraki's, and notably, Muraki's only known friend. He is often seen wearing a highly distinctive and ornate kimono. His habitual use of a traditional Japanese kiseru pipe and practice of kendo are also characteristic traits. Oriya is highly skilled with the katana. His feelings towards Muraki are intense, though whether these are romantic remains ambiguous. In the latest continuation of the series, he is shown caring for Ukyou, Muraki's childhood sweetheart.
Despite usually being portrayed as a neutral or sympathetic figure in the narrative, Oriya actively collaborates with Muraki. He assists Muraki in covering up his murders by leveraging his connections with high-ranking officials. In return, Muraki helps eliminate problematic individuals among the women at his brothel. Oriya's dual role as both a protector and enabler adds complexity to his character, making him a fascinating element within the story.
