A deadly virus sweeps the earth, leaving behind only children and vampires. Yuichiro Hyakuya and the other orphans are captured by these vampires and are forced to provide them blood in order to survive. Fed up, they plan on an escape, but...

After his escape from the vampires, Yuichiro learns that humankind hasn't perished. Determined to get his revenge, he joins the Japanese Imperial Demon Army. Four years later, Yuichiro feels his training is enough, but his bad attitude gets him suspended.

A student sneaks into the Forbidden Chamber, where the army keeps a demon for training. To show how dangerous a demon is, Shinoa takes Yuichiro and Yoichi there, but her plan fails when Yuichiro ignores Shinoa and starts to fight the demon.

Mikaela, who was thought to be dead, was actually turned into a vampire by Krul and is working with them. Meanwhile, Yuichiro starts his first day at the Extermination Unit's training school, but soon gets into a fight with one of his classmates...

Eager to obtain the Cursed Gear, Yuichiro tracks down Guren and persuades him to provide him a chance at the Contract Ceremony. Passing Guren's test, Yuichiro, Kimizuki, and Yoichi put their lives on the line to make a contract with the demon kings.

Yuichiro, Kimizuki, and Yoichi begin their Contract Ceremony to obtain their own Cursed Gear. The demons attempt to take over their bodies, and while Kimizuki and Yuichiro manage to subjugate them, Yoichi fails the trial and becomes a human-eating demon.

With the addition of a new member, Mitsuba, to the squad, they head to Harajuku to find a vampire settlement and destroy it. When they arrive, they see a girl being chased by the Four Horsemen of John. Knowing it's the vampire's trap, Yu goes to save her.

With the information obtained from the little girl they saved, Yuichiro and his squad goes to the subway station where the vampires are in order to free the people. However, they quickly learn that everything was a trap from the start...

After saving the captured people from vampires, Yu and his unit reach Shinjuku. However, by the time they reach there, the war had already begun and some vampires had gotten through. To prevent Shinjuku from falling, they must fight off the vampires.

Learning that Mitsuba, Kimizuki, and Yoichi are in a pinch, Yu and Shinoa rush to their rescue. Meanwhile, Guren and his troops fight off the vampire's main forces, but Ferid's strength seems to be out of their league, cornering Guren in a tough spot.

Finally, Mika and Yu reunite, but their circumstances does not allow for much time. Mika tries to "save" Yu from the humans, who have been experimenting on him, but Yu wants to save his squad. Torn between Mika and his squad, something in Yu is awakened...

Trying to figure out what happened to Yu, Shinoa tracks down Guren and asks what he’s conspiring to do. However, Guren doesn't answer and keeps it a mystery. When Yu finally wakes up from a seven-day-coma, he explains he doesn't remember what happened.

Yu is caught in the middle of a political fight between Guren and Kureto Hiragi. However, Yu's determined to take care of his family - new or old. He assures Guren that he's on his side no matter what, and turns to him for help in saving Mika.

To start the training of the Cursed Gears, the Shinoa squad moves outside the wall to keep the damage to a minimum in case their demons get the best of them. Yu and Kimizuki must overcome their trauma to prove their psychological strength to their demons.

Kureto orders a suicide mission to Guren; wage a war against vampire nobles in Nagoya with only 100 men. Guren needs all the help he can get and brings the Shinoa squad into this mission. Meanwhile, the vampire main units also prepare to head to Nagoya.

When the Shinoa squad arrives late, they realize just how serious this mission is for Guren. Knowing this is an impossible mission where many will die, Guren puts his emotions aside and orders his men to not necessarily survive, but to win.

The Shinoa squad and Narumi squad join forces to carry out their mission - to kill the Fifteenth Progenitor, Lucal Wesker. While they succeed in their mission without losing anybody, others were not so lucky. Nine teams fail and were taken as hostages...

The Shinoa squad re-learns the hard cold fact that it's very possible to lose comrades, but there's no time to mourn. They must move on to go rescue the hostages. Right after their departure, Mika and the other vampires arrive to Nagoya as well.

Guren, Shinoa, and Narumi squads arrive at the city hall and see the hostages. Knowing it's a set-up, they still decide to go save the hostages, but Guren and Shinya are way over their heads with Crowley, as they struggle just to run away from him.

Shinoa's squad goes to save Guren, but unfortunately, they run out of time. Reluctantly, they leave him behind and retreat, but Yu just cannot bring himself to do that. Instead, he takes more of the Curse Stimulant Pills to go save Guren himself.

Thanks to his "experimentation," Yu makes a miraculous recovery and once again, goes back to save Guren. Pushing too hard, Yu nearly becomes a demon, but Kimizuki stops him by force. The squad carries Yu out and heads for safety, but then encounters Mika.

Yu and Mika are finally reunited, but the injuries Mika had sustained from fighting the Demon Company threatens his life. Determined to keep Mika alive, Yu tries to persuade Mika into drinking his blood... Even if it means Mika will become a true vampire.

After escaping, the remaining survivors of the Moon Demon Company get to the rendezvous point. Instead of continuing with the rescue, their orders are simply to "standby." Enraged, they decide to ignore the orders and go to save Guren, when Kureto appears. Apparently, Kureto has other plans.

Kureto plays his trump card: Kimizuki's younger sister, Mirai. Mirai is revealed to be inside the container and emerged as an angel of the Fifth Trumpet. After doing battle, Mika escapes with Yu, Makoto, and the rest of Shinoa Squad. Shinoa declares they all quit being members of the Japanese Imperial Demon Army.