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...

The memory of that terrible night is fading away: not a trace is left, and a brand new desk is placed in the biology room, as if nothing had happened. On her way home from school, George takes Saya to the grave of the Miyagusuku family, on a hill overlooking the sea colored by the sunset. George talks about his past and his meeting with Saya. Back at Omoro, David reveals to Saya that she is the only living being who can defeat the chiropterans, as the creatures like the one that attacked her at school are called. Saya is shocked, but a new menace is just approaching, its eyes shining red...

George is seriously injured and is taken to the emergency ward. Full of anger, Kai takes out a Colt M1911 that his father was keeping secretly hidden, and goes alone after the man -or whatever it was- responsible for that hell, ignoring Riku who tries to stop him. Saya runs around town looking for her brother, when she meets Hagi. Now the young girl must take a decision. And there is no time for hesitation, because Kai is in immediate danger...

David and his group go after George, who had been taken away by the U.S. military, when they learn that there is a secret facility in Yanbaru. Perhaps George is there. When Kai hears this, he asks if he can go along as well, however...

Saya and her team infiltrate the Yanbaru laboratory. David had learned that the U.S. military is conducting experiments underground to build artificial Chiroptera. There he discovers a mysterious keyword called "Delta 69". Then, a Chiropteran swoops down on Saya's party underground, where they can take no refuge. In order to escape from their subterranean trap, they will have to defeat the creature. Who can save Saya and her party from this desperate predicament?

On a ship leaving Okinawa, Riku hears about the tragic event that took place, and so he confines himself in his cabin. Kai tries to comfort Riku, but he doesn't even respond. Saya feels that she is solely responsible for her family's misfortune. Seeing Saya, Hagi takes out the sword and tells her that the key to take back her past lies at the end of the continuous battle. Meanwhile, Okamura, a reporter for the Ryukyu Daily who was investigating the random killing and came to focus on Yanbaru, finds an empty case of Bordeaux wine in the dump yard of an industrial waste disposal company...

Saya infiltrates a girls' boarding school, the Lycee des Cinq Fleches. Hagi too sneaks in, disguised a gardener. Saya learns from her roommate Ming about a legend of a phantom who fell in love with the prettiest girl from the school and who presented her with a blue rose flower.

In Hanoi, Kai and Riku encounter a beautiful girl, Mui, who lost her left leg to an unexploded bomb that had detonated. In the meantime, David and his group analyze the photos of the past phantom incidents at the lycee and find out that the past victims all had black hair and Oriental complexions. They realized Saya was lured out deliberately. Meanwhile, in Naha, Okinawa, Okamura prepares to go to Vietnam on a paid holiday. Then, from the belongings left by his late photographer father, who covered the battlefields, Okamura finds a photo...

In the morning, as Saya comes into her classroom, she finds a blue rose.

Students are murmuring about the phantom legend that has been the gossip at the lycee. Saya and Hagi sneak into a rose garden beside the church where it is said the blue roses were in bloom. And they find steps leading to the underground...

An annual ball is being held in the lycee. Students, guardians and guests in formal attire are gathered in the school cafeteria when Saya arrives in a dress she borrowed from Min. On the dance floor, Saya meets a young man named Solomon, who asks her for a dance. As the music starts, David reaches the entrance to the basement surrounded by blue roses...

Saya and the others follow a container cargo carrying Diva who was transported out of the lycee. The operational unit of the Red Shield, Clara, Spencer, Rogers and McCoy, joins the pursuit. They go upstream on the Mekong River and head toward the experiment farm of Les Cinq Fleches Pharmaceutical. The farm had collected children from all over Vietnam. Mui, Riku and Kai were among them. But Saya and her friends are not aware of this fact as they get ready for the showdown...

At the experiment farm of Les Cinq Fleches Pharmaceutical, Saya is surrounded by child Chiroptera. But confronted with a mysterious humming coming from nowhere, the howling of the Chiroptera and a choking smell of blood, the girl goes berserk, and swings the sword at anything that comes into her view without even distinguishing between friend and enemy...