Manga by author Takeuchi Sakura

Karigari Hiroshi is a total robotics geek/genius who really likes this one girl, Marie. He's too shy to ask her out, so he becomes obsessed with creating a perfect android copy of Marie. He succeeds perfectly in creating Marie, an android with the intelligence and heart/emotions of a human and who looks just like Mari (though with different colored hair). Of course, Karigari never really considered the implications of such a thing...