Short story. Number twenty-two of Tales of the Executioners, stories about the elite vampire "police force".
To protect themselves from one another in the citadel, the Executioners took on human slaves - or guard dogs,. Fifty years later, with no attacks, the vampires have decided to get rid of them. To protect the immortal's secrets, the law says the humans must be destroyed. They're only humans, so why does it bother Migina so much?