虚ろなるレガリア, Utsuro Naru Regalia, Utsuronaru Re Gallia, The Hollow Regalia: The Girl Is a Dragon, the Boy Is the Dragon Slayer

On that day, a huge dragon appeared in the sky over Tokyo, and this was the beginning of the collapse of the nation of Japan. The appearance of the monsters called "deceptive animals" and the "massacre" that ensued around the world caused the death of the Japanese people and turned the whole of Japan into a lawless zone occupied by the armies and criminal organizations of various countries. Yahiro is one of the few Japanese survivors. Bathed in the blood of a dragon, he has acquired immortality and spends his lonely days as a "collector" of artifacts from the uninhabited ruins of Tokyo. Yahiro is visited by twin girls, Juli and Rose, who claim to be art dealers. They asked Yahiro to retrieve a mysterious being called "Kushinada" that has the ability to follow deceptive beasts. A new story of dragons and dragon slayers spun by a boy and a girl who met in an abandoned town is about to begin!