Kasumi and her younger brother Kiriya were born into a family that has served as ninjas for generations, dating back to the Warring States period. Returning from a mission, they find their father mortally wounded by an unknown attacker, and he soon dies. Vowing to avenge him with their own hands, the siblings track down the suspected killer's hideout and successfully infiltrate it. They are just one step away from settling the score when Kasumi finds Kiriya with a blade pressed to his throat. With her brother's life at stake, she has no choice but to submit to rape...