In order to save her sick younger sister, Aria, Cassmire Crisis chose the harsh life of a mercenary, fighting battles and staining her hands with blood to earn enough money for Aria’s treatment. Despite the dangers and sacrifices, everything Cassmire does is driven by her desire to protect the only family she truly cares about. However, after suffering a serious fall, she suddenly regains memories of her previous life—where she had once been Aria’s cruel and abusive stepsister.

Horrified by the person she used to be, Cassmire swears that this time things will be different. Rather than becoming the villain destined to hurt Aria, she becomes determined to shield her from the tragic future written for her. Knowing that Aria is fated to endure endless suffering, Cassmire once again takes up her sword, ready to fight against destiny itself in order to stand beside her sister as her strongest protector.