Mao is an unusual young girl that wears a small white dress with roses on her head.
She has no eyebrows, no upper eyelashes, thick lower eyelashes and sideburns that grow to her jaw. On her rear is a small tail (approximately 5 cm long).
Mao is an agreeable and playful child. She is constantly seen playing with other children at the park, not bothered in the least by her appearances and other quirks. Although she doesn't talk often, she greets everyone she meets.
Despite only being a child, Mao seems to have pushed things so that her mother would meet her biological father.
Mao is only able to speak in reverse and according to her mother, has never spoken normally in Japanese. However, when she meets her biological father, she begins to talk normally with him; When she walks, her footsteps are silent and everything she steps on becomes soaking wet.
Mao's Heart has taken the form of a tail. If it is touched, her body will instinctively camouflage, blending into its surroundings. According to Heaven's Door, this could be considered a visible Stand ability and not a genetic trait.
Mao was conceived through an anonymous Sperm donationW from Obanazawa to Mai.
Nothing about her life is known, but it can be inferred that despite her difformities, Mai still loved her and she lived a calm life free of bullying yet. At one point she befriended Tomoya, Obanazawa's son.
Mao is presented to Rohan Kishibe at the beginning of her story, but upon examination he doesn't find anything wrong with her, as she is born the way she was supposed to be. He thus takes his leave without trying to turn Mao into a normal human.
Later, Mao plays a prank on her mother by shedding her skin and disguised Toyama as herself, frightening Mai who then rushes toward Tomoya and Obanazawa. It is implied she did it so that her mother and Obanazawa could properly meet each other.