For You in Full Blossom (2007)

Japanese-American track star Mizuki Ashiya transfers from a school in California to Japan, but not to just any old school. The school is Osaka High School – an all male high school! Mizuki Ashiya must disguise herself as a boy, all to get closer to her hero Izumi Sano, a high jump athlete who attends Osaka High.

Now with short hair, flattened chest and deeper voice, Mizuki becomes roommates with Izumi Sano, but trouble soon starts to brew. Izumi Sano discovers by accident that Mizuki is a girl and falls in love with her, but Mizuki is unaware of the fact. Complicating things, fellow classmate Shuichi Nakatsu starts to develop feelings for Mizuki, unaware that she is a girl!