One year ago, an alien spacecraft crashed into Tokyo Bay. With no means to return, aliens obtain Japanese citizenship and begin a home-stay program with regular families and schools. They are given the name "DearS," meaning "beloved friend."
However, Takeya, an opinionated teen, doesn't trust the aliens one bit. But when Takeya encounters a mysterious girl who is cold, hungry and wrapped only in a blanket, he takes pity on her. As he brings her home to care for her, he finds that she is quite possibly one of the DearS. Add an alien cat-girl, an over-sexed teacher, and this DearS considers Takeya her master, life is beginning to become a little more than he can handle.