Kaya is a civilian survivor introduced during the final season of Attack on Titan, known for her deep connection to the late Sasha Blouse. Originally from a small village within Wall Rose, Kaya's life was shattered during a Titan invasion when a Titan devoured her mother right in front of her. She was rescued from this grim fate by Sasha, a member of the Survey Corps, who risked her own life to lead the girl to safety. Following this trauma, Kaya was taken in by Sasha’s family, the Blouses, and came to live on their farm, finding a new home and a surrogate family.

Kaya is generally depicted as a calm and quiet individual who does not readily display her emotions. She is not quick to bond with others, making her eventual friendship with Gabi Braun and Falco Grice notable to the other orphans living at the Blouse estate. Despite her reserved nature, a powerful and defining trait is her deep admiration for Sasha, who she views as a heroic older sister figure. This admiration shapes her core motivation: to emulate Sasha by saving people in need, regardless of who they are. This idealism drives her actions when she discovers that Gabi and Falco are enemies from Marley. Rather than turning them in, she chooses to protect their secret and help them return home, directly stating that this is what Sasha would have done.

Kaya's role in the story is significant as a living embodiment of Sasha's legacy. Her existence serves as a constant, poignant reminder of Sasha's bravery and kindness. Furthermore, she is a crucial catalyst in Gabi Braun’s character arc. After overhearing Gabi and Falco arguing, Kaya brings them into her home, offering them food and shelter. She later takes them to the ruins of her old village, where she confronts Gabi with the raw, personal cost of the conflict. Kaya asks Gabi to explain what her innocent mother, who never left the island, could have possibly done to deserve being eaten alive. This confrontation forces Gabi to confront the flaws in her own indoctrinated worldview, challenging the idea that all Paradisians are "demons" worthy of death.

Kaya’s key relationships are central to her development. Her relationship with Sasha is one of idolization and gratitude; Sasha is her hero and moral compass. Her relationship with the Blouse family, including Sasha’s parents Artur and Lisa, is that of a beloved adopted daughter. The most complex relationship, however, is with Gabi Braun. Initially acting as a kind host and protector, Kaya’s feelings turn to violent rage when she learns that Gabi is the one who murdered Sasha aboard the airship. In a shocking moment, the quiet girl grabs a knife and attempts to stab Gabi, only to be restrained by Sasha's grieving father. Later, amidst the chaos of the Battle of Shiganshina, Kaya is cornered by a Titan and is saved at the last second by Gabi. In that moment, she briefly mistakes her savior for Sasha. This act of rescue forces a fragile reconciliation. Kaya later admits to feeling like a "devil" for wanting to kill Gabi, while Gabi confesses to her own sins, and they begin to see each other as individuals rather than as enemies.

Over the course of The Final Season Part 2, Kaya undergoes a significant but tragic development. She evolves from an innocent, trauma-scarred child clinging to her savior's ideals into a young woman violently confronted by the brutal realities of a cycle of revenge. Her attempt to kill Gabi represents a complete, if temporary, loss of the merciful values she sought to embody. Yet, by the end, after being saved by Gabi, she begins to reconcile with her own darkness. Kaya possesses no notable combat abilities or special powers; her strength is purely moral and emotional. Her significance lies in her perspective—she is one of the clearest examples of a "normal" civilian on Paradis, whose life has been destroyed by Titans, and whose capacity for both extraordinary kindness and terrible vengeance reflects the series' core themes about the nature of hatred and forgiveness.