Mahou Shoujo Ore

A quick rundown summary by yoshi-x2:

15 year old girl is a newbie idol in love with her best friend’s brother who is also a popular idol. 
But she runs into a scary yakuza guy and finds out her mother was an ex-magical girl, the yakuza was her mascot. Her love interest gets kidnapped by demons that look like burly men with cute squirrel heads. So she contracts the yakuza to become a magical girl, which in this story means she turns into a handsome guy in a magical girl outfit. And her love interest shows an attraction towards her magical guy form? But her best friend (her love interest’s sister) turns out to be in love with her and later also becomes a magical crossdressing guy to save her life.

Thus their manager is a magical girl geek and decides to make them into an idol unit.