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.
Being of Asian and Caucasian descent, Aya displays features from both her Japanese mother and her American father, with her narrow eyes and facial structure in contrast to her blue eyes and platinum blonde hair (although it is possible that her hair is dyed; most likely it is naturally black as she does have dark highlights).
While on occasion she isn’t too timid to dress in anything fancy, Aya has a casual, modest manner of attire. This is mostly due to the fact that it’s not practical to enter the field in shorts, skirts, and dresses (unless circumstances catch her by surprise). For the most part she dresses fairly simple and her casual attire consists of either black or white tee-shirts, and jeans. In colder weather, she tends to dress in her leather or jean jacket.
Aya is attractive, though she never uses sexuality to an advantage. Instead she relies on her cocky personality when dealing with people. She is lithe in figure, but not frail; she is fairly agile, and while she’s not exactly super strong enough to lift monoliths, she is by no means weak, either.
In The 3rd Birthday, Aya appears much younger because her mitochondria awakened at twenty-five. She looks as though she has not aged a day since, and could very well possibly be considered ageless due to her awakened genes.
Aya tends to be pretty sarcastic, cold, and brooding, though she isn’t without a sense of humor. It can be said that she fits more into the “deadpan snarker” category. It doesn’t help that Aya has a bad habit of not being able to take people seriously sometimes, particularly when they express any sort of interest in her; she tends to brush them off. It’s easier for her to pretend that people are just being insincere most of the time.
In any case, she prefers to keep things professional — mostly where a professional relationship is concerned such as her line of work, and very rarely does she ever like to get herself involved in any intimate affairs. Surprisingly, however, she can be pretty patient. It’s just that when her patience finally runs thin that she has a danger of losing her temper, going against that professionalism and letting her thoughts and emotions get ahead of her.
Aya can be gentle and nurturing, almost maternal — especially with children. She does like kids, regardless of the fact that she’s never had any herself and she treats Eve Brea in a caring, motherly manner. She approaches with a welcoming nature to most people.
She’s often self-sacrificing. This could be considered her greatest strength or weakness, as she has a penchant for putting the wants and needs of others before her own wants and needs. If someone is in danger, she can be pretty compulsive without always thinking things through. For instance, while working for MIST she developed this track record for acting recklessly and going against orders.
There is one thing that she is not proud of: The guilt that weighs down on her. This is most likely the result of various incidents: her surviving the car accident that killed both her mother and her sister and being the sole survivor of the opera massacre that led into the New York Blockade Incident. As well, fighter pilots acted as a shield for Aya so that she would live to fight against Eve. One could very well interpret Aya’s inclination for self-sacrifice as a product of her survivor’s guilt. Aya dislikes it when people put themselves on the line for her, no matter how inevitable it is.
Aya feels somewhat alienated, being so different from everyone else with her superhuman mitochondria abilities. At times, she considers herself a monster; fearing of becoming the monster that Eve said she would be, and the fear of hurting the people she loves follows her. For that reason, and the fact that her Parasite Energy had a way of making the people around her uncomfortable, Aya doesn’t make a habit out of using her powers in front of other people.