Idol Pretender(2011)

Chinami Eita wants to become a true man so he can confess to his secret love, the school idol Yuika. He tries to achieve that by beating the crap out of everyone he can. However, when he has a cold and accidently takes the wrong medicine, he is turned into a girl. An incredibly cute girl. In order to get the money to turn himself back into a guy he starts an idol career and - surprise - he meets Yuika who also wants to become an idol and starts to get enchanted by his manner ...