Moe was not born of the Kuroki Clan originally, being the clan is rather young in itself. Rather, she was born in the Land of Grass to a family of Kemonoken, the Maki. Being of the eldest three of the family, she was focused on heavily, yet, compared to the rest, she was born physically weak and showed no talent for Taijutsu. No Beast school they went to would perform the ritual to convert her chakra to ki, saying it would be a waste of whatever she could ever potentially be to try to force someone as physically weak as she to take on their traits.
Due to her inherent weakness, Moe was something of an outcast, even amongst her own family. She always had the feeling that she was being ridiculed behind her back, and she doubted she was wrong about that a lot of the time. Despite this, she stayed with her family throughout her childhood and did what she could to be useful. It all came to a head, however, one night in the midst of a family dispute. Moe was incidentally struck and knocked back and, in the heat of the moment, ridiculed to her face about her weakness. After a while of argument, she stormed out the door. Her family figured she'd only gone for a walk, and even she figured that would be all she was doing, yet she found herself not stopping. She continued walking until she had left their home village and then their region and eventually the country as a whole.