The war never stops: in a different time, on a different battlefield, hiding deeply into the folds of History... They are called Chiropterans. They can change their form and disguise as human beings, but they are not. They are immortal creatures that feed off blood.

An organization, named Red Shield, has been fighting to exterminate this pestilence, and the struggle has now evolved into something of a much bigger scale.

Okinawa, Japan. Year 2005. Now.

Saya Otonashi is a high-school girl living peacefully with her family - with one exception: she has no memory of her life except for the past year. One day, a startling event causes her happy life to shatter into pieces.

An enemy to destroy, a mission to accomplish - the vortex of an ancient struggle is dragging Saya back to her destiny. A young and handsome cello player in dark clothes appears - his name is Hagi. The moment he hands Saya a Japanese sword, History starts a new course.

Will Saya be able to restore her memory and find her own identity?