Hel, the ruler of the underworld, deceived Odin, the supreme god. Loki, the god of cunning, helped her capture Odin in the realm of the dead. The Valkyries who were supposed to help Odin failed the task and were captured by the demons, becoming their sex slaves.

The plot centers on the story of Yuto and Erica, a brother and sister who grew up without a mother. Their mother died, and their father, busy with work, could not devote enough time to them. That's why Yuto and Erica were often alone.