Pandora's Box is Opened

Once there was a young girl. She was tasked to protect a box that contained the most powerful evil in the universe, but she failed and was cursed for that wrong doing. 1000 years latter she must pretend to be a boy so the people after her power gained from the curse cannot find her. A certain thief wants to stop the people who are after her. Will the Kaitou learn the truth or fail.