Chizuru Yukimura heads to Kyoto to search for her father, finding herself attacked by mad men before they are cut down by members of the Shinsengumi who mistake her for a boy and take her into custody for interrogation. Upon learning that she is a girl and the daughter of a doctor who developed the Water of Life elixir that turns those that drink it into invincible blood lusting berserkers called Furies (羅刹, Rasetsu, lit. Rakshasa), the Shinsengumi decide to keep her as an aide in their search. In time, as the Shinsengumi aid the shogunate in the Bakufu, Chizuru begins to develop a bond with the Shinsengumi and its aloof member Toshizo Hijikata. However, as time passes, Chizuru and Shinsengumi confront a mysterious faction who claimed to be demons and that Chizuru is also a demon with her father revealed to be experimenting on the Water of Life to create the Furies to conquer the human race.