Chizuru Yukimura is the daughter of a Japanese doctor who vanishes during a trip to Kyoto.
To search of her father, Chizuru travels to Kyoto to investigate his whereabouts but in her search she unexpectedly witnesses a member of the Shinsengumi transform into an a Oni/Ogre. Because of this the Shinsengumi decides to capture her for questioning.
(Source: PS2 Game Description & Wikipedia)