"My full name is Mahoro Andou. I'm going to be nineteen this year. I was born in Ebisu, Tokyo. Because of my father's work from when I was three to when I was fourteen, I moved from place to place. My family consists of my parents and two sisters for a total of five. This spring, I graduated from high school and was hired by Vesper Human Resources and my first job is as a maid in Misato-san's house. I want to do my best to be useful so everyone please bear with me." (episode 02)
From the above description, Andou Mahoro seems to be a perfectly normal human girl, doesn't she? But this isn't really the case. In fact, she's a battle android, originally created nine years and two months ago in Ebisu Underground to fight the alien organization named SAINT. She has been trained in different extreme environments (arctic, desert, etc.) According to VESPER, her creator, she is the ultimate weapon against the so-called invading forces. She is fast, cunning, and resourceful if she needs to be. That's why she's undefeatable.
However, that is only one side of her personality. When she's not fighting, she has a sweet and gentle disposition. She's childlike; she gets excited at what humans would think as simple things and/or events. For example, her eyes would light up (not literally, of course) when she sees the different colours in the sky as the sun sets; a bright smile is on her face while she's wearing a puffin costume as she traipses in the arctic or while she chooses which classic movies to watch. Her superiors, the scientists and military officials who designed her, firmly believe that she has a pure heart, even purer than a human's. They're right. She's certainly more virtuous, pure, and benevolent as most humans.
Mahoro decides to work as a maid after being discharged from VESPER. She has most of her armaments removed except for one because it's linked to her vital functions. It's her ultimate weapon and her doom for it discharges her life energy whenever she uses it. She chooses to work for a guy named Suguru. She feels that it's the least she could do. After all, she was the reason why his Dad, Commander Misato, died. You see, a rampant alien robot took him as a hostage and while Mahoro didn't want to destroy it in fear of hurting him, she had no other choice. Besides, he ordered her to eliminate the target, even when he knew it would also include him. So with a heavy "heart," she obeyed his last request. (He was, after all, her superior.) This tragic incident is forever etched in her memory.
As a maid, she does her job well. She cleans up the house -- which has accumulated so much mess over the years because of neglect -- without complaining. In fact, she manages to restore it into a more livable and newer-looking, place. Not only that, she is also an excellent cook. Her skills as a battle android aren't wasted in the kitchen; she uses the sharp daggers strapped to her thighs to slice vegetables and such in midair. She can even create delicious meals using few ingredients. Chizuko, Suguru's genki friend, adores her so much because of her talent.
Anyway, she's very determined in making Suguru comfortable in a, ahem, different way. One time, she goes into the bathroom, stark-naked, and begins scrubbing his back with a washcloth.(He's shocked, of course!) It isn't because she's a pervert, mind you.(After all, she scolds Suguru for stashing porn under his mattress and for oggling at women's breasts all the time!) She just doesn't know that she's not supposed to.
Mahoro can be quite self-conscious at times. She's not comfortable around women with ample bosoms because hers are smaller. She has even wished for bigger breasts not once, but twice! It never crosses her mind that despite her "physical flaw," she has as much allure as any other busty women. Why else would Suguru's friends turn into a puddle of teenage hormones whenever she's around?
Oh yeah, she has a black panther mecha-support named Slash.