Two hundred years ago, the Grim Reaper discovered that collecting souls could help him attain immortality. Greedy for eternal life, he created Larvae—monsters that aimlessly devour human souls—and scattered them across the globe. Aiming to obliterate the harmful Larvae, Lemuria, the Grim Reaper's sister, established the Argent Cavaliers and the Lemuria sect.

Cyan, a knight of the Argent Cavaliers, vowed to protect Lenette Lemuria, the Lemuria sect priestess' granddaughter, when he was little. So when a malevolent force threatens Lenette's safety, Cyan—desperate to save her—gets tricked into making an unfavorable deal with the Grim Reaper. Stripped of his humanity but determined to protect Lenette from future harm, he leaves everything behind to join forces with Jade Lemuria, a Larvae himself. Filled with a strong conviction, Cyan and Jade set out to protect the people they hold dear by eradicating the Grim Reaper once and for all.