|Alignment:||Black Moon Clan|
|Lives:||Nemesis, later Tokyo (anime only; after being purified by the Silver Crystal)|
|Occupation:||Member of the Spectre Sisters|
|Family:||Berthier, Petz, Calaveras (sisters)|
|Aliases:||Koan Kurozuki, Koan Azabu|
|First Anime Appearance:||An Angel? A Devil? Mysterious Girl From the Sky|
|First Manga Appearance:||Act 15 Shinnyuu SAILORMARS|
|First PGSM Appearance:||N/A|
|English Name:||Catzy (DiC dub), Catzi (Mixx manga), Koan (Kodansha manga)|
|Actors:||Wakana Yamazaki (anime); Satsuki Yukino (Crystal); Alice Poon (DiC dub 54-57), Mary Long (DiC dub 58-65, 79); Claudia Lenz (Viz dub)|
Koan was a member of the Black Moon Clan and the youngest of the four Spectre Sisters. She accompanied Rubeus and her sisters to 20th-century Earth in order to locate Chibiusa and find the Silver Crystal.
Koan was the most conceited and most ambitious of the Spectre Sisters, as well as the most developed in the anime. She was constantly making up her face, bemoaning her looks, teasing her elder sister Calaveras, and shopping as a human for new cosmetics and clothes. Koan's greatest dream was to become the Queen of Crystal Tokyo - with a King Rubeus by her side. Much of this fantasy was fueled by her belief that Rubeus loved her like she loved him, a fantasy which Rubeus did nothing to discourage.
As the first sister to appear, Koan became the one most engaged in finding Chibiusa (as opposed to simply capturing Crystal Points, which she only did once). This was a job that Rubeus often trusted her with, and the more she failed, the more determined she became to kill Chibiusa and win Rubeus' love.
Koan, did not have the same respect for her elder sisters as Berthier, who always referred to Calaveras and Petz as "oneesama" (御姉様; elder sister). Despite this, she seemed to truly love her sisters, as shown through her determination to purify the others as well.
Koan's missions led her to unsuccessfully infiltrate the Hikawa Shrine no less than three times, which made her reluctant to go there. Nevertheless, she willingly went to the shrine in episode 70 to kill Chibiusa, even after Rubeus displayed his complete distaste for her. She almost succeeded, even with the interference of Sailor Mars and Yuuichirou Kumada, because Koan avoided Mars' attacks and ended up breaking the Senshi's ankle. Only the interference of Tuxedo Mask allowed Koan to be defeated, and when she was beaten again, Rubeus came and publicly humiliated her, telling her she was no longer welcome and giving her one last present to use on the shrine and the Senshi - a bomb which would also kill her in the process.
Distraught at Rubeus's rejection of her, Koan was willing to use the device but was stopped by the other Sailor Senshi. Angry that she failed even at killing herself, Koan tearfully attacked the Senshi and was almost taken down by a knee thrust from Sailor Jupiter. Sailor Mars, however, took the hit for her after seeing that Koan had only been used by Rubeus and asked Sailor Moon to heal the evil in her. Koan was subsequently turned into a human and would later help her other sisters become human as well.
- Dark Fire - An attack in which Koan threw blue fire at her target. She could either throw a stream of fire from her hands or launch multiple fireballs, similar in appearance to Sailor Mars' Burning Mandala.
- Dark Power - An attack which strongly resembled Dark Fire in appearance; it was used to infuse the Hikawa Shrine with Dark Power.
- Koan Dark Power Flip - A double team attack used by Koan and her Droid Dumble during their attack on the Hikawa Shrine.
Koan first appeared in Act 15 of the manga, where she was in charge of 001: Operation Recruit. Disguising herself as a T·A Academy for Girls student named Koan Kurozuki (黒月紅安), she recruited people to the Black Moon by foreseeing their deaths and then promising them a peaceful passing if they joined her. Unfortunately, those who agreed and bore the crescent sign would then spontaneously combust, as they were most likely unable to handle the power.
After finding one of the school's teachers who had suffered this fate, Sailor Mars confronted her, but was trapped in Koan's flame barrier. Though Sailor Moon used her new Moon Rod to destroy Koan, she was unable to break the flame barrier, and Sailor Mars was abducted by Rubeus.
Koan appeared in chapter four of the video game Sailor Moon: Another Story, having apparently been turned evil again, along with her sisters. She was the first to attack the Senshi on the Black Moon UFO. However, instead of being purified, she was killed by the Sailor Senshi.
- Dark Fire
- Koan was named for the mineral kermesite, known in Japanese as "koanko." Among other places, kermesite is found in chocolate.
- Her civilian last name Kurozuki (黒月) means "black moon."