The supernatural mystery story follows Yukimura, an okinaga who looks 18 but is actually 88 years old. He joins a newly hired Ministry of Health, Labour and Welfare official named Akari Fusegi to stop a serial killer — and seek revenge. Yukimura's former lover was murdered by the so-called "Sheep Killer," who only murders on Christmas during the Year of the Goat every 12 years. The long stretches between the killings means that only an okinaga like Yukimura could be the culprit.