Katase Renna

Ai's rival who goes by the name "Bloody Renna" and who attends Shichiri Academy. She is a daughter of a very rich land owners, which helped her build a team of 500 with her network of contacts and money. Her fighting abilities are inferior to that of Ai's and Maki's, however, she is much smarter than both of them.

Spoiler

The real Renna is when she lets her hair down.