One day someone broke into to Aika's home and her mom heard it and told her to take her sister and ran away. So Aika and her sister got out of the house heard their mom screaming and then the house exploded. Aika and her sister contiuned running but they stoped to lake and there was a demon and the demon killed Aika's sister. Aika tried ran but failed she would have died if slayer didn't save her.