When the senshi go to the park for a picnic Chibi-Usa's hat blows away and she goes chasing after it. As she runs after her hat she passes a pale girl with black hair and amethyst eyes. The girl also runs after the hat and catches it just before it goes into a lake. (Most likely that duck pond that frequently shows up.) She then proceeds to promptly colapse gasping to the ground. Then she returns Chibi-Usa's hat and introduces herself as Tomoe Hotaru. Chibi-Usa also introduces herself and they become fast friends. Then Kaolinite attacked someone also in the park, releasing her demon. Chibi-Usa transformed right in front of Hotaru. During the ensuing scuffle she gets scraped up and after it all Hotaru heals a gash on her knee. After this they steadily become better friends.
She is the daughter of Doctor Tomoe. Her mother died when she was very young, possibly during childbirth. He was originally a very nice man, but drew into himself after his wifes death. One day when Hotaru was about six she was watching her father working on an experiment when it backfired, killing her. This bad guy appears and tells Professor Tomoe that if he gives him his soul he will save Hotaru. So Tomoe, of course, agrees. Tomoe is then possessed and so is Hotaru. Although Hotaru is not consciously aware of the prescence of Mistress9.
Hotaru with the cats.
Hotaru
Hotaru in her school uniform.
Hotaru in a cute lil dress.
Hotaru in another dress.