After being possessed by Germatoid, Professor Tomoe chose his daughter, Hotaru Tomoe, to be the host of Mistress 9. She needed Pure Heart Crystals to increase her power, which is why Kaorinite and the members of Witches 5 continued seeking out Pure Hearts. She demanded him to collect Pure Hearts after the Holy Grail was obtained by Sailor Moon, which Tomoe first interpreted as collecting valuable hearts (by Mimete's standards) and then focused shortly on collecting large quantities of them. As her power grew, she gained more control over Hotaru's body, which culminated when Kaolinite helped Mistress 9 absorb Chibiusa's Pure Heart. This caused the true awakening of Mistress 9, causing Hotaru's body to transform by growing older, letting her hair grow out extremely long, and her outfit chang