Black Wings, Kaminari is a fictional manga and anime series created by Chiaki Koizumi. Rain is a big fan of the series, as is Chanel.
The following text was taken directly from a page in the webcomic.
The manga’s story begins in a kingdom called Tori that floats high above the rest of the world. The people of this land are born with wings however, making their distance from the surface below hardly a problem.
Now typically, the people of Tori are born with white wings, but on a rare occasion, they might have black wings instead. Once very long ago, a single man with black wings nearly overturned the kingdom which led to a very longstanding superstition that black wings represented evil. Superstitious as it was though, the idea was taken very seriously. So much so that any baby born with black wings were simply cast from kingdom before they had the chance to do any damage… and before they could fly. Barbaric as it was, no one ever contested it. The people feared and hated the black wings and what it represented, and were unwilling to ever allow one with them to exist again.
Then Princess Kaminari was born; a child of the royal family bearing black wings. Unwilling to sacrifice their daughter but too ashamed to show her to their people, the king and queen told the people of Tori that she did not survive childbirth. Instead, they locked her away in the castle basement in a place completely cut off from the outside world. For fifteen years, Kaminari only knew her mother and father and one single room. She was still given nice clothes, and good food, and books to read and was very much comforted by her parents, but as far as Kaminari knew, they were the only three in the world.
It happened to be on her sixteenth birthday that Kaminari heard a great deal of commotion from outside. Voices she’d never heard before in an uproar. She’d never thought to escape before, due to her unwillingness to displease her parents, but she had to know if what she was hearing was real. And with that, she escaped, and stepped outside for the first time… just in time to witness the “banishment ritual” of a newborn with black wings.
Without thinking, Kaminari ran past the crowd (who all backed away from her, completely unaware of where she’d come from) and she leapt of the edge of the land after the child. However, life in a single room left her wings largely useless though, and she failed to catch the child for she could not fly. Rather, the best she could do was slow her falling. The landing was still harsh and painful, but she managed to survive.
She landed in a small farming village called Chikyu, where the people were familiar with Tori’s ritual (as they ended up being the ones burying the “banished”), but this was the first time they’d ever seen one with black wings as old as Kaminari. They told her all about the ritual, and showed her the cemetery where hundreds of black winged children rested. They told her they didn’t know who she was, but that she must have been important to have survived up there as long as she had.
Kaminari felt horrible; she couldn’t rationalize that she could possibly be so much more important than hundreds of others just like her. The way she saw it, they died for her. And being the gentle soul as she was, Kaminari swore that she would save someone in honor of each grave present. With that, she left the village on a journey to find and help others in need, even though she was the only one on the surface world with wings (black or otherwise) and she knew nothing of any society outside of books.
BWK is currently being made into an anime. It will begin airing the summer after Rain graduates (i.e. next summer in Rain-world) .
The anime will be simulcast (broadcasted over two or more forms of media, in this case TV and the Internet) in Japanese with English subtitles. 
The anime's plot will possibly differ from the manga's , presumably because the manga is still going.