A girl named Rei and Mirai, her little sister, are dragged to the afterlife of Purgatory by an unknown entity. Scared and confused, Rei tries to lead them home when they are attacked by a terrible monster. To protect her little sister, Rei unlocks the hidden strength within her. With it, she fights against the dead souls of Purgatory.
However, this power turns against her. Rei accidentally kills Mirai with her own hands, thinking she is an enemy.
Devastated, Rei desperately mourns what she has done. Sensing an opportunity, two Demons appear and whisper into her ear...
