Shiro no Keiyaku

From Aerandria:

Shiro is a white crow. Because of his unusual color, he’s often bullied by the other black crows. One day, he’s hurt badly because the others ganged up on him, and he was saved by a girl. Moved by the girl’s gentle heart, Shiro asked a devil to let him turn into a human. However, there’s one condition: Shiro will have to do at least one bad deed a day, otherwise, his body will crumble. Can Shiro really fulfill this contract?