Yumi Fukuzawa is an ordinary first year student at Lillian Girls' Academy. By chance Yumi meets second year student Sachiko Ogasawara, who is a candidate to become a Red Rose. Sachiko later offers her rosary to Yumi Fukuzawa which signifies she will become an older sister to Yumi. Meanwhile, Yumi, who already looks up to popular Sachiko, is perplexed why she is picked. A festival named "Cinderella" then approaches, which is run by the Yamayuri Council. Conflicts between the older and younger sisters soon begins ...
