An epidemic of unknown origin strikes mankind, killing all adults and rendering the youngsters at the mercy of the vampire kind. Four years later, Yūichirō Hyakuya and his friends make a daring attempt to escape from the vampires, unaware that a mortal trap awaits them.

After passing the final test, Yūichirō and his classmate Shihō Kimizuki obtain their own Demon Weapons, but when Yūichirō's friend Yoichi Saotome ends up possessed by his weapon, the duo must find a way to bring him back to his senses without killing him.

Yūichirō and his friends introduced to a new member, Mitsuba Sangū, and are then dispatched for his first mission as part of the Moon Demon Company, but when they spot a little girl in distress, Yūichirō ignores orders and rushes to rescue her, despite being warned that he is just being lured into a trap.

Yūichirō and his companions arrive at Shinjuku to help repel the vampire offensive, while Guren's party spots Mikaela and Ferid, and decides to face them.

Mikaela attempts to escape, taking Yūichirō with him. However, seeing his friends at the mercy of the vampires, Yūichirō goes out of control when a dreadful power emerges from him, threatening allies and foes alike. Shinoa manages to stop him but he falls unconscious.

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 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.