OVA/Artificial Girls/Romance Titles

Enter a world when a new stream of crime has been introduced, the destruction of specialized human appearing robots known as "Third Types", which are neither cyborg nor android. Meet Ross Sylibus, a cop who is trying to escape his past where his partner was killed by a cyborg. To do this, he transfers to Mars only to find himself face to face with Armitage, a tough female cop who is hell bent on stopping the robot murders. As they continue their investigation and the murders continue, Armitage reveals herself to also be a third type robot. Now that Armitage is an official suspect, Ross must come to grips with the fact that his police partner was not a human, only masquerading as one. Can he find Armitage before it is too late? What is the secret of the third types? Why is someone trying to wipe them out?

(Taken in part from AnimeNFO) It's in the not too distant future. One day Nuku-Nuku dropped in and began to live with the Natsume family. Having lost her memory, Nuku-Nuku assumed the identity of a beautiful girl named Atsuko Higuchi. She was so beautiful and gentle, and besides, she was such a great cook that Ryunosuke, 14, was all smiles. However, after her arrival in town, a series of mysterious incidents started to happen in Maneki City - Experimental machines running haywire, roaring fighter aircraft flying low, mass destruction in the city. In every case, a mysterious girl was spotted at the scene of the incident. Who is this mysterious girl?