Kaolinite (called Kaori Night in the manga and Kaorinite in the English anime) is the loyal assistant of Professor Tomoe, and is also greatly infatuated with him. She first appears in Act 24 of the manga and Episode 90 of the anime.

A difference between two variations is Kaolinite's treatment of Hotaru: while in the anime Kaori frequently provokes and mocks Hotaru, in the manga she shows concern towards the girl. Hotaru, however, feels that Kaori's presence in the family home is a sign that she does not know her place.

Kaolinite demonstrates several powers throughout the series, including levitation, teleportation, limited shape-shifting, and using her hair as a weapon (similar to Mistress 9).

In the anime, she is the first of the Death Busters to openly attack people who possess pure heart crystals, using the bio-engineered Daimons she helped create. Her goal is to find the three Talismans, which (unbeknownst to her) are possessed by Sailors Uranus, Neptune, and Pluto. Sailor Mars, Sailor Mercury, and Sailor Jupiter were all targeted by her monsters. In episode 102, she discovers the brightness of Sailor Moon's Pure Heart Crystal and goes after it. The Sailor Senshi rally against her, and she is subsequently defeated by Sailor Uranus, whose "World Shaking" attack causes a glass related attack she was using against the Senshi to feedback on her, encasing her in a pillar of glass and causing her to fall from the Tokyo Tower. In episode 113, she suddenly reappears as Hotaru Tomoe's guardian, calling herself Kaori (except in the dub, where she is still Kaorinite). It is later revealed that Professor Tomoe himself had managed to revive her. However, she feels that her place has mostly been filled by the Witches 5, and is jealous of them as well as Hotaru. By episode 123 she is filled with hate, and steals the Pure Heart of Sailor Chibi Moon, Hotaru's best friend. The crystal is ingested by Hotaru's possessed form, and she awakens as Mistress 9, the Messiah of Silence. The last words Kaolinite hears are congratulations from Professor Tomoe, before she is thrown into an electrified wall by Mistress 9 for "having served her purpose".

In the manga, Kaolinite's role is slightly different. As opposed to the anime, where her origins are unknown, it is revealed in one of Professor Tomoe's flashbacks that she became Kaolinite after being struck by random lightning during a chaotic storm that occurred as the pair attempted to reconstruct the maimed body of his daughter Hotaru. When she rises from the floor, her eyes are shining. Her title is "Magus Kaolinite", Magus being a position that all of the Witches 5 aspire to reach. A privilege of the Magus position is that the use of the Tau Star System's crystal is accessible. In the manga, it is Kaolinite, not Tomoe, to whom the Witches 5 answer. She sees them in no way other than servants, demonstrating annoyance when Mimete appeals to her for help. It is implied that she wishes to be Pharaoh 90's partner in place of Mistress 9, something Mistress 9 is aware of and views with amusement. When Mistress 9 does awaken, she orders Kaolinite to eliminate the Sailor Senshi. She succeeds in subduing the Guardian Senshi but they are freed by Uranus, Neptune, and Pluto. Reunited, the Senshi confront Kaolinite in the President's office of Infinty Academy, and she transforms into a Daimon. She is then destroyed by Super Sailor Moon's "Rainbow Moon Heartache" attack.