The legendary creature Kumiho is a member of the elusive Skin-changer race, capable of changing their physical form between two or sometimes more creatures. Nobody (including Moon herself) knows exactly how old she is. Whenever she transforms, all her cells are reborn. This effectively stunts most of the aging process. If Moon stays in her animal form for long enough, she also loses touch with all parts of her human self. She then has to relearn all aspects of human behavior, language, and convention. This trying experience is luckily something Moon has only had to undergo once (as far as she knows), having found it necessary to stay in her fox-like form for a prolonged period in order to evade a group wanting to capture and experiment on her.