Kuroi otome: A

Orphan girl Mei is adopted by a wealthy family and receives the ticket out of the orphanage. The girl finds herself with a sister who has arrived at the family under similar circumstances. They bond and become close. Things take a turn for the worse, however, when the family's fortunes take a nosedive allowing the family to keep no more than one of the girls. That means someone has to trod back to the orphanage. Well, neither is volunteering.