Mercurio

At first she appears to be a clumsy, but cute engraver working for Yamamoto. However in truth 2 personalities exist inside the body. The cute and kind side being a demon and the ruthless side and original owner of the body an enchanter. The demon side is in love with Haruhiko, while the enchanter is trying to kill him to prevent him from repairing the unit holding the demon side inside her body. (Source: Wikipedia)