Aya was born in Boston, Massachusetts on November 20, 1972. She is of mixed ethnicity; her father whose name is unrevealed is a journalist, is Caucasian while her mother who is known as Mariko was Japanese. This gives her a unique appearance as she boasts many Asian facial features, such as the shape of her face and eyes, while possessing blue eyes and fair blonde hair. Aya was born with an eye defect. She had a sister named Maya who, along with her mother, died in an automobile accident in or around December 1978.
After Maya's death, her organs were preserved, which allowed for one of her corneas to be transplanted into Aya, in 1979. At the same time, one of Maya's kidneys was transplanted into a young girl named Melissa Pearce. Unknown to any of the doctors, Maya Brea's mitochondria were highly evolved and began changing Aya and Melissa's genetic structure.
As a young woman, Aya studied criminology at the University of Virginia and was involved in their ROTC program, but any record of military service is never mentioned within the game. She later became a detective with the NYPD 17th precinct. Within the first 6 months of working at the precinct, Aya became involved in an incident known as the New York Blockade Incident to the general public. As an officer, she became part of the "father and daughter" team where she was partnered up with Daniel "Bo" Dollis, a veteran cop, who can be considered overly protective of her at worst.