Mary, a failure princess, cannot use magic. A political marriage has been arranged for her.. Finally, she's useful as a member of the royal family――Mary thinks positively. However, she's arrested at the fiancé's unveiling party for ridiculous crimes and sentenced to execution. Betrayed by her parents and even her brother, Mary flees with her older sister, the only ally she has. However, she's unable to escape and has been killed along with her sister by the most powerful magician, the "Arcana User". However, at the edge of death, Mary's power awakens. The power she gained was the Arcana of "The Death", which allows her to eat corpses and strengthen herself.