Koan is the youngest of the four Spectre Sisters, a group of female warriors serving the Black Moon Clan. She accompanies the commander Rubeus to twentieth-century Earth with the mission of locating Chibiusa and the Silver Crystal. Her name is derived from the mineral kermesite. In the events of Pretty Guardian Sailor Moon Crystal, Koan infiltrates a school where she senses a kindred spirit in Rei Hino, the reincarnation of Sailor Mars, due to their shared affinity for fire and psychic abilities. Koan is portrayed as confident and ambitious, fully loyal to the Black Moon Clan and eager to prove her worth to Rubeus. She uses fire-based attacks, most notably Dark Fire, in combat. Unlike her counterpart in the earlier anime adaptation, Koan does not undergo a redemption arc; she remains a dedicated antagonist. Her key relationship is with Sailor Mars, whom she recognizes as a rival with similar powers. When Sailor Mars uncovers Koan's true identity, a battle ensues in which Koan attacks Sailor Mars with fire. In retaliation, Sailor Moon and Tuxedo Mask defeat her using the Cutie Moon Rod. Koan's role in the story is that of an initial obstacle who helps reveal the larger threats of the Black Moon Clan. Her abilities include pyrokinesis, psychic sensitivity, and the power to generate destructive flames. She is ultimately eliminated before the clan's deeper schemes are uncovered.