In Japan, during the Karai's Path story arc, Karai brought Koya on the mission to reclaim the Kira no Ken, where Koya struggled with her temper and self-pity. When the sword was found, Koya removed a small bird-shaped talisman from the same cave.
Later in the Prey story arc, the talisman had a strange effect on Koya, speaking to her and causing her to be struck by lightning. When she attacked the spirit in the talisman, she obtained spectral wings that allowed her to fly again.
After Karai and company returned to North America, they visited the Turtles during their retreat in Northampton in the Leonardo Macro-Series issue. Koya immediately sought revenge against Leonardo, only to find Leo immediately taking responsibility and apologizing for inflicting such a life-altering permanent injury on her. Koya grudgingly accepted that she could never be satisfied with revenge against Leo as long as he had no intention of putting up a proper fight. Far from resuming a fight with her, Leo sympathized with Koya's inner disquiet, treating her with enlightened respect. There would be no vengeance during their meeting.
Koya is expressive, and is frequently excited and eager to hunt down her prey, and often speaks of eating the Turtles. She is particularly hostile towards Leonardo, whom she saw as a traitor, and her hatred for him only intensified after he crippled her in the Gauntlet. Those feelings later faded after he took responsibility for his actions and his own trauma, leading to a mutual understanding and respect for each other. It is later implied by Big Lita that she has feelings for Leo, the two of them romantically together in the future- though she loudly declares that a lie (Ironically calling for Leo to handle the issue).
She and Bludgeon have a sibling-like relationship, and they look out for each other. Bludgeon is often the voice of reason for her, preventing her from running wild, or attacking without a reason aside from "being enemies".
- Koya is specifically a brown falcon, a species native to Australia.
- She is partly inspired by the Japanese folktale of the Sworded Falcon, and is named after the village, Koya, that the falcon terrorized.
- She was meant to have blue eyes, to tie her into