Not much was known before her imprisonment, but Yamori developed an arrogant and sadistic personality that mirrored in her in her love of torture. She is a manipulative and deceitful ghoul who would be violent in order to get what she desires.
She has a strange habit of finger cracking from which she would, unintentionally, pass to Kaneki. Despite her brutish, cruel, sadistic and violent nature she was somewhat carefree. She also would gain attachment and love for someone she’s torturing.