Saya and her team infiltrate the Yanbaru laboratory. David had learned that the U.S. military is conducting experiments underground to build artificial Chiroptera. There he discovers a mysterious keyword called "Delta 69". Then, a Chiropteran swoops down on Saya's party underground, where they can take no refuge. In order to escape from their subterranean trap, they will have to defeat the creature. Who can save Saya and her party from this desperate predicament?

Saya and the others check in at a hotel where they are supposed to meet up with others. While David is out doing some research, Riku comes down with a fever. Saya stays with her brother and takes care of him, but in this situation, Liza questions Saya about her true intention to fight the Chiroptera. Why does she kill them? Is she not getting others involved in the battles by killing Chiroptera? Saya, who is still confused about the real meaning of the dreams she had in Vietnam and in the Russian tundra, appears unable to find an answer. And then, Liza says something even more shocking...

Finally Saya confronts Diva. The memory of the tragic event that took place at Joel's birthday starts to come back to Saya. And as she screams, Kai dash to the top of the tower...

As Irene starts showing signs of dying, Kai refers to Saya what he was told about Schiff. But for the girl, who firmly believes that her task is to exterminate the Chiroptera, this is the first time she feels desperately far away from her stepbrother. In the meanwhile, Julia isolates a DNA component that apparently does not belong to any known living creature on this planet...

It has been one year since Diva's attack on the Red Shield Headquarters. Kai and the others stay with David's old comrade in the outskirts of London. Passing time brings various changes to everyone. But again, the Chiroptera overshadow the streets of London...

Okamura and Mao inform that Diva's promotional video was planned to be filmed on a deserted island with ruins of a small village on the seaside. David and others head for Christina Island. There awaited James and Corpse Corps, the mass-produced version of the Schiff!

Kai sneaks into Diva's show at the air force base. He is introduced to Diva by Amshel and offered to join as Diva's Chevalier. As Kai refuses, Diva bares her fangs. Just in time, Saya and Hagi arrive, but Amshel and Nathan's raid hinders them to advance. At the same time, David spots Julia in the base and follows her.

Solomon, accompanied by Nathan, shows up before Diva. He transforms his right hand into blade and charges to slash her. Meanwhile, Julia continues her study on D-base in Diva's blood, and realizes that the effect of synchronicity caused by Diva's singing could infest the entire world with chiroptera...