Miiru Kamishiro is a character introduced in the second original video animation and the final four volumes of the Fushigi Yugi manga. She first appears as a freshman at the college attended by Taka, Keisuke, and Tetsuya. Shortly after enrolling, she joins Keisuke's Ancient Chinese Mythology Club, where she examines the mysterious book known as The Universe of the Four Gods. She expresses belief in Keisuke's account of another world inside the book, where his younger sister was drawn in and became the Priestess of Suzaku.

Beneath this seemingly ordinary student exterior, Miiru is actually the second of the Shitennou, the four Demon Gods who serve the powerful being Tenkou. She is the older sister of Ren, and like him, she was granted supernatural abilities by Tenkou and can travel freely between the real world and the world of the book.

Miiru's role in the story is that of an antagonist and spy for Tenkou. She uses her powers to manipulate and harm others, often by controlling blood. Specifically, she can implant parasites into a person's bloodstream to control them from within, or she can craft dolls out of blood and use these constructs as tools to influence a person's actions. These abilities make her a dangerous opponent, capable of subtle infiltration as well as direct confrontation.

Her primary relationship is with her younger brother Ren, with whom she shares a bond as fellow servants of Tenkou. Her alliance with Tenkou defines her motivations, as she carries out orders to further Tenkou's objectives. There is no recorded development or change in her character over the course of the narrative; she remains a loyal agent of Tenkou throughout her appearances.