Niche - Tegami Bachi
Born of Lilith
Lag found Niche at a train station on his way to his Bee Interview. She was a "letter", but the address on her mailing label was incomplete and she was scheduled to be "abandoned" in two more days. Lag offered to take her to her new home even though he was on a deadline for his Bee job interview. While traveling, Lag found she had multiple names, so he named her Niche after where he found her - in a niche at the station.