Kisa has been treated like a monster her whole life just because she was born with cat ears and a tail. Her twin sister Hina was born normal as you can get.
Kisa's village treated her like how naruto was treated in the leaf village, if not worse. Plus she is really sick and has a weak heart. Her village beat her, starved her, raped her, and after they had their fun they banished her from the village, and took all her stuff, so that she was left nothing.
Her parents didn't care for her and treated her like the rest of the village, not even her own twin stood up for her.
Kisa has many secrets and emotions bottled up inside, and she knows she'll break. But there's no one to listen to her. That is till she finds her self in Konoha also known as the village hidden in the leaves.