S-Girl: A scientist buried in his work to avoid the pain of his wife's death, he brings a robot home which looks just like his wife. The robot carries the burden of making her two daughters "happy". Tzu-Yu, a scientific girl who inherited her father's talent. She has not only to face the huge changes caused by her robot mother, but also the pressure of the competition. Moreover, the romance between her and the gifted transfer student Yi-Hsiu, making her sip the sweet and sour taste of growing up.