Emiko, arrives at the house of Kaien Cross. When she witnessed her parent's and brother's brutal slaying, by a pureblood. Zero, who lives with Kaien and his daughter Yuki, is drawn to this girl. But why? Who is she? Emiko and Zero become friends, often acting like each other. While Yuki, is left on the sidelines. In Zero's eyes, the only one that matters is his Emi.