Melia, a girl unable to use magic, was separated at an early age from her grandmother, her only family. Since then, she has been treated unreasonably by the family that took her in. In the midst of her continuous painful days, she has a fateful encounter with Douglas, a knight directly serving the princess who arrived from the royal capital. Douglas is searching for "Mana Substance," which harbors the magical power needed to cure the princess's illness, while Melia lives believing she has absolutely no value. The curtain rises on the story of a thousand-year oath revolving around these two—!