Owari no Seraph: Nagoya Kessen-hen
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. That 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!
(Summaries provided by MyAnimeList.net)