Boy meets girl

The monsters are winning. Saya Otonashi thought she could battle against the chiropterans, defeat the undead monsters, and avenge the life of her adoptive father.

But the creatures, led by Saya's twin sister Diva, have struck a fatal blow: their attack on Saya's adopted brother Riku has left him infected with the vampiric curse and destined to transform into a chevalier, a half-human abomination with an unquenchable bloodlust.

Saya finds herself drawn to the papers of nineteenth-century explorer Joel Goldshmidt, and his long-forgotten journal.

As Saya reads Joel's diary she learns more about her past of murder and horror, the perverse origins of the Red Shield organization, and the grotesque destiny she and Diva share.