Since ancient times long past, this world has been ruled by two tarot cards: 
Diablos Tarot—The tarot of the devil that feasts on the souls of living humans and uses that nourishment to bring countless pain and suffering. 
Elemental Tarot—The tarot that draws its energy from the power of nature in order to oppose the Diablos Tarot. 
Girls chosen from 22 different bloodlines become the wielders of the Elemental Tarot, plunging themselves into this secret battle. To maintain the balance of this world, while carrying unbearable guilt… 
Are they executioners? Or saviors? This is the story of the long, long battle fought by girls who cannot escape the fate they bear.
 
(Source: Anime News Network)