Mahou Shoujo Ore

This story is about a 15-year-old girl who 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 that her mother was an ex-magical girl, and 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. On top of that, her love interest shows an attraction toward her magical guy form. Her best friend turns out to be in love with her and also becomes a magical cross-dressing guy to save her life.

Thus, their manager, who is a magical girl geek, then decides to turn them into an idol unit.

(Source: MU)