Rei first appears as a miko at the Hikawa Shrine, and is shown to have an affinity with two crows who live there. It is revealed in the manga that as a child, the crows "told" her that their names are Phobos and Deimos (the same as Mars' two moons). In the manga, she is portrayed as imperial, ancient, conservative, old-fashioned, traditional, serious, disciplined, and practical, having contempt for men and disliking modern romantic relationships.