Itsuka Tenma wo Kiryu Majo

This is a side story to Itsuka Tenma no Kuro Usagi. It follows the angsty loner Liene, along with her two classmates--big-breasted Clara and cheerful Chiya--as they train to become first-class witches. In order to become a first-class witch of the Temperon Crowley association, they first have to make a contract with a demon, which costs the thing they cherish the most (generally assumed to be a girl's virginity). Liene wants to become a first-class witch so that she might have a chance of meeting the parents who abandoned her as a baby. However, she's going to have to learn that she can't do it alone. She'll have to cooperate with her first real friends, Klara and Chiya, and with her new demon companion Pelty.

(Source: MangaHelpers)