In 2012, the world allegedly comes to an end at the hands of a "man-made" virus, ravaging the global populace and leaving only children under the age of thirteen untouched. At the same time, the vampires emerge from the recesses of the earth, likely followed by age-old horrors of the dark thought only to be myth. They sweep the earth and claim it in a single violent stroke, subjugating the remnants of humanity and leading them beneath the surface to safety. This "protection" comes at the price of "donating" blood to their captors, not knowing that they are vampires. At the age of twelve, you and your friend and fellow orphan Mikaela plotted to escape along with the children in Hyakuya Orphanage. However, this resulted in Mikaela sacrificing himself in order for you to escape and be saved by members of the Moon Demon Company, an extermination unit of the Japanese Imperial Demon Army. Four years later, you dedicate your life to destroy vampires and seek revenge against them for killing your "family." At the same time, it is revealed that Mikaela survived and plans to find you.