Ямаґамі Мамімі

Although one of the minor characters exclusive to the anime version of the Sister Princess series, she has proven to be a popular character among viewers. First appearing as a fellow classmate of Wataru going to Promised Island, it turns that she is sent by someone to keep an eye on Wataru, and apparently to break him apart from his sisters. Part of this includes getting stuck as pretending to be Wataru's 13th sister, although she really isn't. (Note: she is related to one of the characters in the series.

Read the later episode summaries if you want to know who it is) As she spends more time with Wataru and his sisters, she realizes how much he means to the girls and how much he cares about each and every one of them, including her. When it comes to indecisiveness and problems that Wataru seems to run into, she helps to set him straight and offer her honest opinions and advice. It was disappointing to fans of Mami that she wasn't a prominent character in Sister Princess Repure, mainly due to the fact that Repure was more structured on the original stories of G's magazine. However, she does make a brief appearance as one of the girls working at the bakery where Yotsuba and Rinrin had followed Wataru.