Japan, Okinawa Prefecture, Okinawa City, Koza District. Saya is a senior high school student, and with her best friend and classmate, Kaori Kinjo, she is a member of the track and field team at school. She lost her memories of her life beyond that of the past year, but she is living peacefully with her family. His father, George Miyagusuku, runs a pub called "Omoro." She also has two brothers, Kai, hot tempered but actually kind and committed to his family, and Riku, who is good natured and loves to read. But Saya's unruffled life is about to change: when she accidentally meets a handsome cellist, Hagi, it is a sign that the wheel of fate has begun to turn...

School. Biology Room. Night. Kai, who has come to pick up Saya, witnesses an incredible scene: her sister covered with blood is fighting with a sword against a creature beyond any description. Then Saya faints on the spot... The next day, the incident is treated as a murder committed by a drug addicted American soldier, and there seems to be no trace of the creature. Taken to the hospital from school, Saya accidentally hears the conversation between George and David, a mysterious man who watches over Saya. And what she hears makes her run away terrified...

As Saya sees Diva's babies, she hopes no one will be hurt. She takes her sword and brings the point up slowly. At that time, the US army was about to carry out a plan to erase all evidence of the Chiroptera...