In order to attain immortality, the Grim Reaper began devouring the souls of the people. To gather more souls, he created Larvae and unleashed them upon the world.

Cyan is a member of the Argent Cavaliers, an order of holy knights founded by the Grim Reaper's sister, Lemuria, that's dedicated to eradicating the Larvae. After meeting Jade, a descendent of the Reaper who is himself one of the Larvae, Cyan decides to leave the Cavaliers and join Jade on his hunt for the Grim Reaper, putting everything - including his humanity - on the line to save Lemuria, to whom he has pledged himself since childhood.