Kaya is a petite young girl with bright eyes and blonde 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 Braus 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.
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 Braus stables and regarded as a good thing.
After being saved by her, Kaya wants to be like Sasha Braus 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.
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 Braus 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.
After introducing them to the Brauses 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 Braus 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.
- "Kaya" is a common surname in Turkey and means "rock" in Turkish.
- In Indonesian, "Kaya" means "rich." This is ironic, considering Kaya lives in a village and a rather small house.