Saya is shown to be a beautiful young teenager with gray eyes that are sometimes red, long natural nails, and black oval-shaped glasses with white thin temples and the rest of it being rimless. She has long black hair that is usually kept up into a low ponytail or low twin-tails in one or two red ribbons that are wrapped around them at the back of her head. She usually wears either her shrine maiden outfit or high school uniform.
Her school uniform consists of a dark grey short sleeved shirt with a Peter Pan collar. It also has red highlights on it. On her right arm, there is an armband that is connected to her right sleeve. She wore a double red tie with a dark grey line around the bottom of it. Near the top of the tie, there is a chain connected on each side of her collar, which has a red lining on the collar. She wears a red pleated skirt that goes just past mid thigh length with some small black lace on the bottom of it. She also wears black socks cut just below the knee and red and brown shoes in a school model.
Her outfit in The Last Dark consists of a dark navy blue sailor uniform with white lining on the collar and ends of sleeves as well as a red bow.
Despite her youthful appearance, Saya is hinted to be much older.
She is initially portrayed as a kind, clumsy and helpful person, acting very cheerful and singing songs in the morning. She loved her friends, her family, and her normal life as well as being dutiful in her family's fighting against the Elder Bairn.
However, It is revealed at the end of the series that her cheerful personality was faked due to an experiment. Her true and original personality is a cold and serious person, often causing troubles to the city and places wherever she goes. She has a very deep hatred towards Fumito Nanahara, and Fumito himself states that she does not care for humans, and wishes to be able to drink their blood, but is unable to due to a contract made with an unknown person.
Saya has displayed abilities far above natural human capabilities. This is most notable in the fact that she has survived numerous battles with Elder Barin.
- Enhanced Endurance: Saya has been shown surviving injuries that would kill a human without question and still be capable of fighting even with said injuries. After having her head blown open by Fumito’s she simply bandages the injury and leaves the experiment site.
- Enhanced Strength: Despite her petite appearance, Saya was capable of holding her ground against Elder Barin’s much larger than her like Cerberus with either a katana, anything sturdy or empty-handed.
- Swordsmanship: Saya has shown herself to be a competent swordswoman although the style she uses is unknown. A majority of Elder Bairns slain by Saya were defeated when she was wielding a katana.
- Intelligence: In battle, Saya is capable of deducing an enemies weakness and fighting style such as with the Eye Elder Barin. When her signature weapon is unavailable she is able to improvise with almost anything sturdy such as a mop handle. In the film The Last Dark, Saya practiced extreme caution around most of the other characters and cautiously refrained from consuming most food and drink which later proved justified.
- Enhanced Speed: When facing off against her father, Saya managed to defeat him with several blinding strikes that severed his arms.
Saya Kisaragi is the daughter of the priest at the local shrine, whose duty it is to slay the Elder Bairns, creatures who drink the blood of humans. It is what her mother did before she died, and now Saya is the only one who can slay them. By day she seems to live a normal life of a high school girl, though Saya does seem to be rather clumsy, and completely oblivious to many remarks that are made around her, especially concerning boys that seem to like her. Since neither she nor her father are capable cooks, she eats breakfast every morning at Guimauve, the cafe next to the shrine.
The owner, Fumito Nanahara gives her a sweet called Guimauve, named after the cafe, as well as preparing her lunch. When she fights, her abilities are human or slightly above normal human abilities, until her eyes glow red. She then seems to become more serious, and much stronger and faster. Her father, Tadayoshi Kisaragi, provides her with a sword with which she fights. As the series progresses, Elder Bairn attacks become more frequent, even occurring during the day and at the school which Saya attends. As more and more people die or go missing, Saya begins to have strange visions and flashbacks, along with headaches that occur when she tries to remember certain things.
A small cute dog appears, who states (Yes, he talks. It is hinted that he is Kimihiro Watanuki) that he is trying to grant her wish. Saya made a promise to protect everyone, but cannot remember to whom she promised. She realizes she cannot remember her mother's name or appearance. This, and some other things, he tries to get her to realize, but she is still unable to remember anything. Tired of waiting for Saya to remember, Kanako Tsutsutori (along with Nene Motoe, Nono Motoe, and Shinichirou Tokizane) try to force Saya to remember by having her drink the blood of an Elder Bairn. Tsutsutori, however, overdoes it, and Saya becomes inebriated. They tell Saya that they are all "cast members" who were hired to play many roles, in which she is the "lead star".
Several characters who were previously thought to be dead are shown to be alive, namely Tokizane, Nono, and Nene. They are confronted by Yuuka Amino and Itsuki Tomofusa, who question why they tried to ruin the project. Fumito Nanahara joins them, and it is revealed that he is the one who arranged for Saya to be brought there. He has been controlling the Elder Bairns by using Saya's blood, and has a Cerberus bairn kill Tokizane, Nono, and Nene for trying to make Saya remember. Saya remembers drinking the blood of the Elder Bairns that she defeated. Every time, Fumito would make Saya forget again. Kanako runs to Tadayoshi, who embraces her before killing her and drinking her blood. Tadayoshi is half human, half Elder Bairn. Saya begins to remember her past self, and of the terms to the wager which she and Fumito had agreed; By erasing Saya's memories and planting fake ones, would she change? Or would she revert to her old, murderous self?
Saya cannot kill humans, and agreed to protect them, but it is not revealed with whom she made this contract, or who made the stipulation that she couldn't harm humans. Saya said she wouldn't change, but Fumito said he would arrange it so she could attack humans if she won the wager. He does not say what he gets if he won the wager. Saya defeats Tadayoshi, crying as he dies and calling him "Father". As Saya chases after Fumito, he leaves a strange bunny Elder Bairn, which Saya slices in half. It multiplies and slaughters the town full of people, many whom are screaming that it was not part of the contract. While still running after Fumito, Saya kills the original, and the rest of the strange bunny bairns die.
Fumito begins to fly away in a helicopter, and Saya jumps high enough to finally kill him, but he shoots her in the head, apparently blowing half her head off. As she falls into the ocean below, Fumito comments, very calmly, that the ingredient in Guimauve was the blood of the Elder Bairns, and he had been told that it tasted like human organs. He wonders if she ever will be able to kill humans, as she could have the real thing then.
As the helicopter flies away, Saya remains floating in the lake. She is still alive, and rests on shore waiting for her wounds to heal. After what seems to be a day or two, Saya rips off part of her school uniform skirt and bandages her still bleeding left eye. The dog remarks that, before Saya was captured, she made a wish: "I want to stay myself". He says he has fulfilled this wish of hers, but it is time for her to reach for the next wish.
As the credits begin rolling, her sword breaks in half. She throws it away, and starts running away from the area, presumably to search for Fumito.
Six months after the incident at Ukishima Province, Saya arrives in Tokyo by train. Aboard this train, an Elder Bairn, later revealed to be the father of Mana Hiiragi, attacks. After viciously attacking him, the creature flees after taking Mana Hiiragi hostage. Saya pursues him through the streets of the city before killing him by plunging a katana through his head, shattering her own blade in the process. As members of Fumito's secret police arrive, Saya flees with the members of SIRRUT, ultimately ending in their headquarters.
There, she meets Kuroto Mogari, benefactor to the organization. He expressed the desire for revenge against Fumito and wished for Saya's help with carrying out this plan. Leaving SIRRUT headquarters with Mana following in pursuit, Saya ends up at a shop where she is greeted by Watanuki. He revealed that he was able to communicate with her in Ukishima through the dog to help guide the return of her memories. Leaving the shop with a new katana to replace the one she had shattered in her previous fight, Saya speaks again with Kuroto, who reveals that he and Fumito are cousins. The Mogari and Narahara families were responsible for maintaining the pact between the Elder Bairns and humans, but Fumito broke that pact and killed both of their families for his own personal ambitions.
Through the information acquired by Hiro Tsukiyama, Saya attends a ceremony at Tsuji Private School, where Fumito was scheduled to give a speech in hopes of assassinating the latter. It was revealed to be a trap, as the Fumito attending the event was an illusion designed to lure Saya to the event. An Elder Bairn attacks, and despite being defeated, it had served its purpose to injure and collect her blood.
After the event, Mana resumed her previous skill at computer hacking, revealing Tower's headquarters in a landfill. Infiltrating the facility, Saya battled through Fumito's guards to reach the basement of the compound. There, she encounters Fumito himself before succumbing a drug that she had unknowingly ingested from the coffee at SIRRUT. Kuroto arrives and reveals that he and Fumito had been working together this whole time, using SIRRUT to lure Saya to Tower headquarters. Fumito reveals that Saya's blood is able to break the pact between the Elder Bairns and humans, causing them to run rampant. After stating that everything he had done was for his personal obsession with her, Kuroto angrily stabs him with a katana. In response, Fumito shatters a vial of Saya's blood in Kuroto's eye, causing him to transform into a pod-like Elder Bairn. As she recovers from the effects of the paralysis drug, Fumito merges with the pod which transforms into a colossal Elder Bairn under his control.
Saya battles with the giant, killing it to come face to face with Fumito. Saya hesitates for a while as he takes her katana and stabs it into his own chest, revealing that he had a long ago tried to turn himself into an Elder Bairns, so he could reach her who made a pact with humans. Fumito, however, failed, and realizing her desire to have her own curse broken was also not fulfilled, he accepts he lost their bet. Her winning prize could not be reached as he promised so he kissed Saya, revealing how he tried and really cared about her race and curse, just before fading away. Saya then laments that, after all, Fumito left her all alone again. Afterwards, it is revealed that she never returned to SIRRUT, with the ending scene a glimpse of her walking through the streets of Tokyo by herself, and Mana wishing that they may meet again.
At the beginning of the series, he is portrayed as the priest of the local shrine, and is raising Saya alone after her mother passed away when she was just entering elementary school. Throughout the series he is shown to care for Saya, supporting her after her fights and being concerned when she doesn't feel well. In the final episode, Tadayoshi kills and drinks the blood of Kanako Tsutsutori, before fighting Saya. As he dies, Saya holds him and cries, calling him "Father", even after learning that they are neither blood-related.
Twin girls, the only difference between them is their hair partings. Initially shown as very cheerful girls who enjoy teasing Saya, they are later hinted at being con-artists, who only agreed to be part of the "main cast" in return for having their criminal activities removed from their records. They do not care for Saya at all, even seeming to enjoy her anguish when the truth is revealed.
Though she was initially viewed as Saya's friend she is revealed to be cold hearted and only cares about her reward for "acting" with everyone else, which is to become Governer of Tokyo.
The owner of the cafe next to the shrine, Guimauve, Fumito makes breakfast and lunch for Saya since she and her father are not capable cooks. When first introduced, Fumito seems to care for Saya a great deal, tending her when she gets sick, bringing food, and once telling her that she is a special person to him. Fumito is actually the person responsible for erasing Saya's memories and hiring the "cast". His motives have something to do with manipulating Shrovetide, a time when demons are allowed to feast on humans.
- In the last episode after the credits, Saya is seen wearing a school uniform similar to the Saya of Blood: The Last Vampire Movie.
- Saya Kisaragi has long hair, which is similar to the hair of the original Saya Otonashi respectively of Blood+ in 1863, and the early version of Saya in the 1972 Vietnam War scenes only.
- Despite major dissimilarities, there are different personalities portrayed between the two Saya's of Blood+ and Blood-C such as their backstory and character. However, they do share some traits, albeit displayed differently. For example, Saya Kisaragi sings whenever she is walking around town while Saya Otonashi plays the cello badly, judging from the reactions of other characters.
- Saya Kisaragi's origins remain cloaked in mystery. Despite this, her origins were unlike Blood+, where Saya Otonashi comes from a chiropteran mummy.
- Saya never calls for a sword in the series except in the opening when she minds control of her cover of the sword. Tadayoshi Kisaragi gives her the sword before her battles, which is similar to the moments when Saya receives her sword from Haji and David in Blood+ and The Last Vampire, respectively.
- Saya Kisaragi have handlers with the Japanese Government in the form of Fumito Nanahara, Tadayoshi Kisaragi and Itsuki Tomofusa during the experiment.
- Ironically, during the final episode, Saya recognizes Tadayoshi Kisaragi as her Father even though she knew they were not biologically related. She still calls him "father", meaning she acknowledges him as a parental figure.
- In Japanese, Saya means "scabbard" ( i.e. the sheath of the sword) or "shell" (such as the shell of the pea) and Kisaragi means "a change". Both meanings are relevant to her as they convey the change undergone by her personality in the beginning of the series.