Yuuichirou Hyakuya meets his childhood companion Mikaela Hyakuya, whom he had long believed dead. During their encounter he learns that Mikaela has become a vampire. Resolute to aid her, Yuuichirou deeply swears to grow stronger so he can defend Mikaela and the allies of the Moon Demon Company.
Kureto Hiiragi receives intelligence that a sizable vampire contingent will assemble in Nagoya to launch an attack on the Imperial Demon Army's principal forces in Tokyo. Under Guren Ichinose's command, Yuuichirou's unit is among several chosen to intercept and eliminate the vampire lords for the greater good.
As the Nagoya operation draws near, members of Shinoa's squad focus on mastering their armaments and refining cooperation. Yuuichirou must acquire the strength needed to vanquish the nobles, rescue his closest friend, and confront lingering doubts that threaten his resolve before he falls victim to the curse of the Cursed Gear. Nightfall heightens urgency, making every moment crucial. and resolve is tested.