After a mysterious virus wipes out ninety percent of humanity, vampires emerge from the recesses of the earth to enslave mankind, treating them like livestock. After growing tired of donating blood in exchange for protection, 12-year-old Yuichiro Hyakuya and his best friend Mikaela Hyakuya plot an escape along with the other orphans. After being the only successful runaway, Yuichiro joins the Moon Demon Company, an extermination unit of the Japanese Imperial Demon Army dedicated to killing off vampires.
Yuuichirou has reunited with Mikaela at the Shinjuku Battle, but Mikaela was turned into a vampire. To save the "family," and to protect his fellow members, Yuuichirou needed to gain knowledge and power. He searched for ways to bring back vampire to human beings, and at the same time, trained hard working on the Cursed Gear. Meanwhile, Kureto calls Guren and tells him a shocking truth: in one month, the main unit of the vampire will start attacking Tokyo. To get a head start against vampires, Kureto orders Guren to go to Nagoya. The noble extermination mission is about to open fire.