Ruby is a black mage, something rarely seen in this kingdom. In a society where white magic users—the Saintesses—are highly valued, black magic has long been scorned as an unknown and savage power. Even in a life marked by mistreatment, her younger half-sister, Saintess Floria, seemed to be the only one who was different. She acknowledged the value of black magic and always encouraged Ruby. However, one day, Ruby discovers that all of that kindness was a lie. Instigated by Floria, Ruby had been using her black magic believing it was for a noble cause, unaware that it was actually being used for human experiments. Accused of those crimes and condemned, Ruby awakens… only to discover that she has returned several years into the past. In her first life, she was deceived and humiliated for using her black magic believing it was for the greater good, until she was ultimately accused and sentenced to death. Now, in her second life, Ruby vows to protect the kingdom from her sister, the villainous Saintess, using her black magic… and this time, she will not allow herself to die!