|I...want to be more like her.|
|— Kaya explains what type of person she wants to be|
Kaya is a petite young girl with bright eyes and light hair which she keeps tucked behind her ears. Her hair is long and straight, ending at her shoulder blades, with straight bangs styled in front. Kaya is originally seen with shorter hair and wearing a simple tunic. After being taken in by the Blouse family, Kaya appears in finer clothes. On the farm she is seen wearing a long sleeve, dark dress with a short sleeved, lightly colored shawl that is cross tied.
Kaya later appears in more formal clothes. She is seen wearing a long sleeved dress with cuffed sleeves and a frilled white shirt underneath. Similar to the other Blouse girls, she wears a ribbon tied in a bow around her collar.
Kaya is a calm and quiet person who does not often show emotions. She does not seem to bond easily with people, as the fact that she gets along with Gabi Braun and Falco Grice is noted by the other orphans living at the Blouse stables and regarded as a good thing.
After being saved by her, Kaya wants to be like Sasha Blouse in which she tries to save people in need, no matter who they are. When she overhears Gabi and Falco admit they are from Marley, she helps cover up their secret identities and even tries to help them find a way back to Marley, despite them being from an enemy nation and Gabi having tried to kill her and accused her and her mother of being responsible for atrocities.
Despite Kaya's kind personality she is not above violence when her loved ones are involved. When it was revealed that Gabi was responsible for Sasha Blouse's murder, Kaya attempted to stab her in a fit of rage.
When Titans appear in Wall Rose, the village is abandoned while Kaya and her mother are left behind, due to her mother having bad legs. After a Titan appears and begins devouring her mother, Kaya is left in a state of shock, and is unable to flee. She is rescued when Sasha Blouse arrives at the village and leads her away. However, Sasha's horse flees without them, and so they are forced to flee the Titan on foot. Sasha has Kaya continue on alone so that she can stay and attempt to fend off the Titan.
Following Sasha's death in the year 854, Kaya and Sasha's parents visit her grave to pay their respects.
After introducing them to the Blouses and eating, the children begin doing chores around the farm. They take a break to eat lunch, and Kaya explains that all of the children on the farm are orphans, who are being supported by the queen as they have nowhere else to go. Gabi accuses them of trying to forget the sins that they committed against the world, and Kaya bemusedly asks if that is what she was taught in Marley. The two are shocked to learn that she knows their identities; Kaya mentions she overheard them arguing earlier, but claims she has no interest in turning them in.
Kaya takes the two to the ruins of her village, and recounts the story of her mother's death at a Titan's hands. Kaya asks them to explain what her mother did to deserve the fate she got, and although Gabi claims that the Eldians have oppressed the world for thousands of years, Kaya repeatedly reminds her that her mother never left the island of Paradis her entire life. As Kaya begins to grow agitated at Gabi's repeated accusations, Falco interrupts and reveals that the invasion was a byproduct of Marley's infiltration of Paradis, and the deaths caused in the process were only incidental. Falco apologizes, but Kaya claims that he does not have to apologize for something his country did.
Kaya tells Gabi and Falco of how she was rescued by Sasha, who put herself in danger so that Kaya could escape. Knowing that the Blouse family has been invited to dine at a restaurant where a Marleyan works, Kaya offers to take them as well to see if there is a way for them to return home. When asked why she would agree to help them, Kaya simply explains that she wants to be like Sasha.
Artur Blouse arrives with his family along with Falco and Gabi to the restaurant he was invited to. As Gabi starts to get nervous, Kaya assuages her fears by telling her that Niccolo is a Marleyan and that he can be trusted. Kaya enjoys the food and a while later, Falco feigns a stomach ache so he and Gabi could meet with Niccolo. Suddenly, Gabi is thrown back to the dining room by Niccolo. He reveals that Gabi is the one who killed Sasha, to the Blouses's shock, and hands Mr. Blouse a knife to kill Gabi. When he refuses and the knife is placed on the table, Kaya takes it and lunges at Gabi but is stopped by a Survey Corps soldier. Mr. Blouse and Lisa hold back a hysterical Kaya, as she cries into their shoulders.
Later, when the Yeagerists arrive to the restaurant, Kaya and the rest of the Blouse family are taken captive alongside those present from the Corps. They are taken to Shiganshina, where the entire group is imprisoned in the district's military headquarters. The Marleyan forces launch their surprise attack on Paradis and as the Jaw Titan fights Eren Yeager on the prison's rooftop, Kaya looks up, in wonder of what the commotion was about. The Blouse family is then freed from prison along with the remaining Survey Corps soldiers by Onyankopon and Kaya flees with her adoptive family under the care of Niccolo. They search for shelter as the battle between Eren and the Marleyans begins to unfold, during which they unknowingly pass Gabi and Falco, who are hiding under the care of Falco's brother Colt. Kaya again voices her desire to avenge Sasha by killing her two former friends, unaware that Gabi overheard her and could not bring herself to face Kaya again. While the battle outside rages, Kaya takes cover with her family in a house while Niccolo stands guard.
Soon after, the family is forced to flee after being discovered by a Titan. However, Kaya is separated after she stumbles and is soon cornered by the Titan an in alley. Before she is devoured, she is saved by Gabi who Kaya initially identifies as Sasha. As Gabi reveals that she came back to search for Falco, soldiers appear and recognize her as a Marleyan. Kaya covers for her by claiming she is a family member which diverts their suspension. As they are escorted to safety, Kaya and Gabi begin to question why they would save one another. Kaya then compares herself to a "devil" for trying to kill her, but Gabi emphasizes that she herself is one for killing people to earn praise. However, both girls are consoled by Niccolo who explains a "devil" resides inside everyone, which caused the world's current situation, and that everyone needs to try working their way past their own evils.
- Sasha Blouse - Kaya was saved from a Titan by Sasha and took in by the Blouses after the destruction of her village and the death of her mother. Kaya looked up to Sasha, saying that her bravery is what inspired her to help Gabi and Falco despite them being enemies. Since being taken in by the Blouse family, she has regarded Sasha as a surrogate older sister. Her death affected her, as she was seen with the Blouse family mourning Sasha. Upon discovering Gabi's role in Sasha's death, she has vowed she would avenge Sasha should the two ever cross paths again.
- Gabi Braun and Falco Grice - Despite knowing all along that they are from Marley, Kaya took them to her home and spent some time with the two. She got close to them, spending her free time with them and confiding about her mother's death. However, after learning Gabi was the one who killed Sasha, she became mad and tried to stab her. While escaping the violence in Shiganshina along with the rest of her adoptive family, she bitterly stated she could never forgive Gabi or Falco for killing Sasha and wished she could kill them both. By pure chance, Gabi and Falco overhear Kaya from afar, and Gabi is forced to see what her actions have caused while abandoning her previous prejudices against the people on Paradis. However, Gabi saves Kaya from a Titan, and in turn, when a soldier questions if Gabi is one of the enemy soldiers, Kaya defends her and says Gabi lives with them; they later talk and come to terms with their own demons. When Gabi goes to rescue Falco, she says farewell to Kaya, revealing her real name and embracing her, mending their relationship.
- "Kaya" is a common surname in Turkey and means "rock" in Turkish.
- In Indonesian and Malaysian, "Kaya" means "rich." This is ironic, considering Kaya lives in a village and a rather small house.