Hajime, from Gatchaman Crowds.
If her background had at least explained how she turned out to be such an uncharacteristically-strange individual, I probably wouldn't be asking this question, but her background is practically non-existent and we never get into her head. She's a character that just happens to exist and seems perfect for just about every aspect that pertains to the context of the story; she's just too convenient. At the end, it seemed necessary for all of the Gatchaman to reflect on how something sucked, and/or how they didn't like/care for her, and now she's the best thing since sliced bread and things couldn't be better.