Sawa Yukimura runs a quiet bookshop in an alternate Meiji-era Tokyo where the Tokugawa shogunate still rules, but by night she serves as an executioner for the secret police force Nue. The last survivor of the Karasumori clan, she carries the clan's blue blood, which lets her take a crow-like form in combat. She hunts Janome, the Kuchinawa insurgent who slaughtered her family, while raising the orphaned girl Asahi as her own sister.