Moujuusei Shounen Shoujo

Moujuusei Shounen Shoujo (猛獣性少年少女) is a manga series by Yumi Nakata. It is serialized in Champion RED.

Plot
High school student Usami Tooru bumped into his classmate Ayabe Reri, one day while taking a stroll. Ayabe is like an idol in their school, but she is a usually a quiet and honest beautiful teenage girl. But by chance that night, Tooru caught a glimpse of her skipping on top of a rail. The next day, Tooru was asked by Ayabe to keep what he saw a secret. How will the relationship of such an unlikely couple play out?