Desperate to save his retainers and friends, Guren makes the ultimate sacrifice and gives up his humanity to accept the demon in his cursed gear, thereby transforming himself into a demon as well. His newfound demonic powers help him protect the people important to him, but the victory is short-lived. Hours later, the Imperial Demons' presumed heir, Kureto Hiragi, takes all of Guren's family and their followers hostage and presents Guren with an impossible choice: track down and kill his childhood love Mahiru Hiragi within a month, or watch as the Hiragis execute everyone in his clan--starting with his father.