Chocotto sisters

Summary: 

    The story centers around a Christmas wish made by Haruma Kawagoe after his mother had suffered a miscarriage, followed by an operation which prevented her from having any more children. Several years later, when Haruma is a college student, a woman on a flying motorbike claiming to be Santa Claus delivers his wish, a younger sister. When he remarks that he made his wish a long time ago, Santa replies that making a little sister takes a lot more time than just making an android, takes his signature for delivery, and departs. Haruma now has a little sister, who comes with her own instruction manual—a manual for how to be a little sister, that is. When she asks him to name her, he calls her Choco, which refers to the Japanese for "manual".