Kaaya functions as an oracle skilled in defensive and healing magic. She encounters Jil following his injuries in combat and heals him at her home. Her primary instrument is a long wand activated by inserting specific small runes and chanting; it enables protective shields, enhancements to allies' agility and strength, healing, insulation, freezing, and limited offensive capabilities such as inducing sleep or destroying barriers.

She is a descendant of Ki, who assisted Gilgamesh in his legendary fight against Druaga, linking her lineage directly to Uruk's monarchy. At the end of the first season, she departs with Neeba under duress, betraying Jil's party to save their lives—an act presented as a reluctant necessity compelled by external pressures.

During the second season, Kaaya reveals her true identity as Ishara, the great-granddaughter of King Gilgamesh and the rightful heir to Uruk's throne after his death. She apologizes to Jil during this disclosure, acknowledging their friendship while emphasizing her concealed royal duties. Her decisions arise from a conflict between these ordained obligations and her personal bonds, especially her connection to Jil.

By the series' conclusion, she ascends to rule Uruk, fulfilling her destined role. Her relationship with Jil evolves into a romantic partnership, culminating in their union during the finale.