There Could be no doubt that those children from the Hyakuya orphanage, Mika, a boy named Yuu and the rest, were, indeed, the test subjects for the Seraph of the End magic research project - something that vampires were forbidden to have anything to do with. There was a rule set up in the vampire world that when vampires discovered Seraph of the End experiments being conducted, they were obligated to destroy the organization conducting them in its entirety.