Ella, the amnesiac last survivor of the Purified, accidentally frees Morrigan, the Demon King sealed away for ten thousand years. Bound by an Empathy Bond that makes them share pain, they become entangled in Heaven's scheme to ignite a war. When Morrigan sacrifices himself, Ella awakens and saves him in return. Together, they expose Heaven's tyranny and overthrow its hypocritical rule.