A 17-year-old piano student from Rogetsu Isle.
Ruka was one of the five girls who were spirited away in the midst of the Rogetsu Kagura. When the girls were found, they had lost all of their memories up until that point, leaving the truth behind their disappearance a mystery. Ruka's parents divorced as a result of the incident, and she was taken to live on the mainland by her mother, Sayaka. Following the successive deaths of two of the five girls who were spirited away, Misaki Asou and Madoka Tsukimori return to Rogetsu Isle. Upon learning of this, Ruka, wishing to regain her lost memories, defies her mother's orders and heads to the island once more.
Ruka hazily recalls a single melody, and each time she plays it, fragmented snippets of memories resurface in her mind.
As she searches the island, guided by this melody, she unravels the secrets behind the song taught to her by her mother and the masks made by her father, moving closer and closer to regaining her past.
A selfish and strong-willed 17-year-old girl.
Misaki was one of the five girls who were spirited away in the midst of the Rogetsu Kagura. Due to her disappearance, she is unable to remember an "important person" she used to be with as a child.
Following the deaths of two of her friends, Tomoe Nanamura and Marie Shinomiya, Misaki heads for Rogetsu Isle with Madoka Tsukimori in tow, led by a girl in black called Miya. She is a descendant of Dr. Kunihiko Asou, the creator of the Camera Obscura, and brings a "camera that can produce images of the past" along with her from the Asou family home.
As she is led along by Miya, she gradually begins to remember her past, and finally reclaims her lost memories of the "important person".
A timid 17-year-old girl who does whatever her friend, Misaki Asou, tells her to do.
Madoka was one of the five girls who were spirited away in the midst of the Rogetsu Kagura. She remembers nothing from before her disappearance.
Ever since the deaths of their friends, Tomoe Nanamura and Marie Shinomiya, Madoka has noticed changes in Misaki's behaviour that worry her.
Despite her concern for Misaki when she declares that she is heading to Rogetsu Isle, Madoka accompanies her there.
In order to remember their pasts, the girls explore Rogetsu Hall, where they formerly stayed as inpatients.
One of the five girls who were spirited away in the midst of the Rogetsu Kagura.
She remembered nothing from before her disappearance. Following the incident, she moved to the mainland and underwent treatment for her Moonlight Syndrome there.
10 years later, she was found dead in a sickroom with her hands covering her face, which was contorted as though she had been crying hysterically.
She appeared to have been listening to a tape containing a recording of a piano song sent to her by Ruka at the time of her death.
One of the five girls who were spirited away in the midst of the Rogetsu Kagura.
She remembered nothing from before her disappearance. Following the incident, she moved to the mainland and underwent treatment for her Moonlight Syndrome there.
10 years later, she was found dead in her room with her hands covering her face, which was contorted as though she had been crying hysterically.
Judging from the state of her surroundings, she seems to have hidden away in the darkness of her room, somewhere she couldn't see the moon, while in a state of panicked confusion.
A former police detective who now works as a private investigator.
During his time with the police, he travelled to Rogetsu Isle in pursuit of Yo Haibara, a suspected serial killer. While there, he discovered that a group of girls had been spirited away, and ended up locating them himself two weeks later. Through this case, he became acquainted with Sayaka Minazuki, who, a decade later, requests his services as an investigator to find Ruka after she returns to Rogetsu Isle.
After catching a glimpse of his long-time nemesis Yo Haibara at Haibara Infirmary, Choshiro becomes convinced that the case from 10 years ago isn't over yet.
As he juggles his pursuit of Haibara with trying to help Ruka, he slowly regains his own forgotten memories.
A doctor, the son of Shigeto Haibara and younger brother of Sakuya Haibara. He is a slender man with the cold, penetrating gaze of a mind reader.
Haibara is wanted for a string of murders resembling human experimentation at the Haibara Clinic in Tokyo, and is being pursued by Choshiro Kirishima, who was previously the lead detective on the case.
Haibara returned to Rogetsu Isle on the day of the Rogetsu Kagura, a festival of great importance to the islanders.
He leads Choshiro towards a certain location, uttering cryptic remarks along the way.
The director of Haibara Infirmary, the only hospital on Rogetsu Isle, and manager of Rogetsu Hall.
As the island chief, he was also the priest responsible for the Rogetsu Kagura.
He had been studying Moonlight Syndrome for many years, and after his wife committed suicide and his daughter Sakuya fell ill with the disease, he began experimenting with treatments that may be considered illegal.
He indulged and doted upon his son Yo, even granting his wish to run a hospital on the mainland.
Ruka's mother, formerly known as Sayaka Yomotsuki.
She is physically frail and largely bedridden. After learning that her husband Soya Yomotsuki was involved with the kidnapping incident, she left him and took Ruka with her to the mainland.
Sayaka, who was born on an island in the vicinity of Rogetsu Isle, is a Guardian - a shrine maiden who uses sound to preserve the peacefulness of people's hearts - and taught Ruka a variety of melodies.
Ruka's father, and Sayaka's former husband.
Soya is a master mask-maker who crafts the masks for the Rogetsu Kagura, a festival to comfort the dead.
Consumed by his determination to master the art of mask-making, Ruka found him strict, frightening and intimidating as a young child.
He is passionately obsessed with completing the "Mask of the Lunar Eclipse", the ultimate mask created by his ancestor, Soetsu Yomotsuki.
A doctor from the mainland who worked at Haibara Infirmary and Rogetsu Hall as the assistant of Shigeto Haibara.
Despite viewing Shigeto's research into Moonlight Syndrome with a degree of appreciation, he harboured doubts about the director's usage of treatments that resembled folk remedies.
Though he may not have been particularly concerned by music and art therapy, he began to question whether they were truly doing the right thing after witnessing treatments employing strange devices and surgical procedures that veered into human experimentation territory first-hand.
A black-clad girl whom only Misaki Asou can see.
She appears before Misaki again and again, asking her if she has forgotten something.
It is Miya's guidance that spurs Misaki to return to Rogetsu Isle.
The daughter of Shigeto Haibara, and older sister of Yo.
She was hospitalised in Room 412, "Frozen Moon", on the fourth floor of Rogetsu Hall.
Her strong capabilities as a spirit medium made her a powerful Vessel. She suffered from a severe case of Moonlight Syndrome, and her symptoms had become so extreme that she was on the verge of blossoming, with the nurse in charge of her care writing that she was unable to remember Sakuya's face.
In order to maintain her sense of self in the face of her illness, she projected herself onto a variety of dolls, treasuring one doll in particular.
A girl who was hospitalised in Room 207, "Orchid Moon", on the second floor of Rogetsu Hall.
She suffered from a particularly severe absence of morals, tormenting the nurses with such extreme "pranks" as cutting people with knives. She appears to have developed a fixation with destruction in order to protect her self from Moonlight Syndrome.
Ayako received preferential treatment from the nurses at Rogetsu Hall due being hospitalised there at the referral of Shigeto Haibara, and also appears to have been on close terms with Yo Haibara.
A woman in black clothing who was hospitalised in Room 311, "Waxing Moon", on the third floor of Rogetsu Hall.
Kageri was a member of the distinguished Sendo family, and wandered the corridors of Rogetsu Hall pushing a wheelchair carrying a doll identical to herself which she called "Me".
In order to preserve her self from Moonlight Syndrome, she became obsessed with dying, and wished to die while still alive. On the day of the incident in which the islanders vanished, she encountered a "dead while still alive" being, the ideal to which she aspired.
An elderly artist who was hospitalised in Room 309, "Faded Moon", on the third floor of Rogetsu Hall.
He was tormented by an assortment of hallucinations, which he recorded in the form of many paintings. He appears to have developed a fixation with painting his visions in order to protect his self from Moonlight Syndrome.
"Yuko" is a pseudonym; his real name is unknown. His works are displayed within Rogetsu Hall's gallery, "Moonlit Window". No visitors ever came to see him, leaving him to spend his days alone at his drawing board, painting in solitude.
A boy who was hospitalised in Room 206, "Wizen Moon", on the second floor of Rogetsu Hall.
His room is a cluttered mess, filled with items he had stolen from other rooms throughout Rogetsu Hall and brought back with him. He proved to be a headache for the nurses, ignoring their scoldings and becoming angry when they attempted to return the objects to where they belonged.
He appears to have developed a fixation with bringing "his things" back to his room in order to protect his self from Moonlight Syndrome.
A nurse who came to Rogetsu Isle from the mainland.
Tsubaki looked up to and admired her mother, who had also been a nurse, and decided to follow in her footsteps. At Rogetsu Hall, she was in charge of the third floor, where Ruka and Misaki were staying. Despite feeling lost in the unfamiliar place, she was a hard worker who went out of her way to assimilate herself into her new environment, and was well liked by the islanders.
Tsubaki was selected to play the role of the "Vessel" in the Rogetsu Kagura, and agreed to participate in the Rogetsu Festival in order to repay the islanders' kindness, but collapsed and died in the midst of the dance. An autopsy was performed to establish a cause of death, but the results were ruled inconclusive.
A group of five girls who were selected as Organs to play the accompanying music for the Rogetsu Kagura.
Each around the age of 10, they were tasked with providing the vocals, flute, drum, strings and bell, respectively, encircling the Vessel as she danced.
The five Organs involved in the performance where a shrine maiden perished also collapsed, but their condition was not life-threatening. However, the incident did appear to have a strong impact upon the girls, such as the vocalist becoming mute, and the flautist never smiling again.