Ryouran Gakuen Kakumeiki: Hyakka Ryouran!

The story takes place in a boarding school for rich girls. In this school, the student council seem to hold an important place in student life, offering great influence to whoever gets elected president. The school also has unique customs, which allow, among other things, (sex) relationship between girls. We get acquainted with Ryouko, a popular girl who seems to enjoy lewd activity with other girls. But since she has a fiancé, her pussy is off limit. One of her friends wants to use Ryouko's popularity to win the student council election. However her plan won't exactly work as planned, because Ryouko decided to run for student council president with the idea to bring change to the Academy.
And thus starts the chronicles of the Ryouran Academy revolution.