"Hakuōki: Otogisōshi" is a 12-episode anime series that serves as a prequel to the "Hakuōki" franchise, exploring the events leading up to the main storyline. Set in the late Edo period of Japan, the narrative revolves around the Shinsengumi, a group of samurai tasked with maintaining order in Kyoto during a time of political upheaval. The story focuses on Chizuru Yukimura, a young woman who disguises herself as a man to search for her missing father, a doctor who has been researching a mysterious elixir known as the "Water of Life." Her journey leads her to cross paths with the Shinsengumi, who are also investigating the elixir due to its connection to a series of supernatural occurrences and the creation of powerful, inhuman warriors called Rasetsu.

As Chizuru becomes entangled with the Shinsengumi, she forms close bonds with its members, particularly the stoic and disciplined commander Toshizō Hijikata, the charismatic and skilled swordsman Sōji Okita, and the calm and strategic Isami Kondō. The group faces internal and external conflicts as they navigate the turbulent political landscape, battling rival factions and uncovering the dark secrets of the Water of Life. The elixir grants immense strength but at the cost of one's humanity, transforming its users into bloodthirsty monsters. This theme of sacrifice and the struggle to retain one's humanity in the face of power is central to the narrative.

The series delves into the personal struggles of the Shinsengumi members, their loyalty to their cause, and the moral dilemmas they face as they confront the consequences of using the Water of Life. Chizuru's presence as an outsider provides a unique perspective on their world, and her determination to find her father adds emotional depth to the story. The plot intertwines historical events with supernatural elements, creating a blend of action, drama, and intrigue. The series concludes by setting the stage for the events of the main "Hakuōki" storyline, leaving key questions unresolved and maintaining a sense of tension and anticipation.