Kasumi is the Goddess of Elements, her clan was been killed by a Sound Ninja she was being saved by the 3rd Hokage (Hiruzen Sarutobi) he decided to let her stay in the Konaha Village.... the 4th Hokage (Minato Namizake) and Kushina Namizake (the wife of 4th Hokage) decided to let Kasumi be their daughter