From MangaHelpers:

This is a side story to Itsuka Tenma no Kuro Usagi. It follows the angsty loner Liene, along with her two classmates--big-breasted Klara 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 lear... More...

From MangaHelpers:

This is a side story to Itsuka Tenma no Kuro Usagi. It follows the angsty loner Liene, along with her two classmates--big-breasted Klara 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. [tethysdust] Less...