She is an Amanto from the Yato Tribe. During her childhood Kagura lived in the slums of a faraway planet with her father, mother and older brother. At one point in her life her older brother Kamui attempted to kill their father Umibouzu, however he failed and only managed to cut off his father's arm. This caused Umibouzu to go berserk and he nearly killed Kamui but was stopped by Kagura. Soon after that, Umibozu left the family. In fear that he might harm her unintentionally just like Kamui, Umibozu left to avoid further destroying his family [1].
While at home, Kagura is left with taking care of her sick mother and she would wait for Umibouzu to come back from his alien hunting work. Kagura calls her mother 'Mummy' and she remember her as a beautiful woman. Her mother died of illness when Kagura was very young.
Knowing her brother and father weren't around, She travelled to Earth to start a new life.
Kagura has a number of pets named 'Sadaharu No.X' before the current Inugami Sadaharu came along. Previous pets all died because of her own inability to control her massive strength and killing the pets inadvertently. 'Sadaharu No. 28' was the latest deceased addition in the form of a dung beetle. 'Sadaharu No.1' was a rabbit.